Ink jet material and process for producing same

ABSTRACT

An ink jet recording material having a high gloss and capable of recording thereon ink images having high color density and clarity, has an ink-receiving layer formed on a substrate and including a binder and secondary particle having an average size of 10 to 300 nm and including a plurality of primary particles of silica prepared by wet method and/or aluminosilicate agglomerated with each other without binder, and can be produced by forming the ink-receiving layer on a shaping base, bonding the substrate to the ink-receiving layer on the shaping base and separating the resultant laminate from the shaping base.

[0001] This application is a continuation-in-part application of Ser.No. 08/842,043 filed on Apr. 23, 1997, entitled INK JET RECORDINGMATERIAL AND PROCESS FOR. PRODUCING SAME.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an, ink jet recording materialand a process for producing the same. More particularly, the presentinvention relates to an ink jet recording material having excellentgloss, ink-receiving property, water-resistance, weather resistance andbeing capable of recording ink images with excellent color density andbrightness and clarity, and a process for producing the same.

[0004] 2. Description of the Related Art

[0005] The ink jet recording system is an ink image recording systemwherein ink droplets are jetted through an ink-jetting nozzle toward arecording material and jetted ink droplets are absorbed in and fixed onthe recording material, to form ink images. This ink jet recordingsystem is advantageous in that full colored images can be easily formedand the printing noise is low.

[0006] The ink usable for the ink jet recording system contains a largeamount of a solvent in which a coloring material is dissolved ordispersed and thus, to obtain a high color density of the recorded inkimages, a large amount of the ink must be absorbed in the recordingmaterial. In the complete absorption of the ink droplets reached therecording material, a certain length of time is necessary. This featureof the ink jet recording system causes such a disadvantage that when theink droplets are continuously jetted imagewise to form ink dots on therecording material surface, sometimes the ink droplets reach a targetdot before an ink dot adjacent to the target dot has been completelyabsorbed in the recording material, and the target ink dot is connectedto the adjacent ink dot so that the resultant ink image becomes unclear.

[0007] Accordingly, if the recording material for the ink jet recordingsystem is to have such an advantage that the ink dots formed thereonhave high color density and brightness and a high clarity, the inkdroplets must be rapidly absorbed therein and even if the ink dots areoverlapped on each other, substantially no blotting of the ink mayoccur.

[0008] When a coated paper sheet is used as a substrate for the ink jetrecording material, at least one ink-receiving layer comprising a porouspigment is formed on the coated paper sheet to control the colorbrightness and sharpness of the ink images from which the image qualityis established and to enhance the color-reproducibility andimage-reproductivity. For example, Japanese Unexamined PatentPublication No. 62-111,782, No. 63-13,776 and No. 63-104,878 disclose anink jet recording sheet having an ink-receiving layer containing primaryor secondary pigment particles (usually, silica or alumina particles)having fine pores, and a binder. Also, Japanese Examined PatentPublication No. 63-22,977 discloses an ink jet recording sheet which hasan ink-receiving layer including an uppermost layer provided with poreshaving a peak size of from 0.2 to 10 μm, and is capable of receiving anabsorbed ink in voids having a size of 0.05 μm or less, and of formingink images with a high quality.

[0009] Currently, due to the rapid spread of ink jet printers, variousink jet prints with a high gloss similar to that of photographic printsare demanded for publications and packing paper sheets. Particularly, incolored prints, film type or coated sheet type ink jet recording sheetswhich have high ink-absorbing and fixing rates and a high ink absorptionare in great demand. To provide the above-mentioned ink-receiving layerhaving an increased porosity, it is necessary to use pigment particleshaving an increased particle size in the μm order or to utilizesecondary particles of pigment. When the size of the pigment particlesis increased, the resultant ink-receiving layer exhibits a decreasedsmoothness and a reduced light transmission. Namely, the resultantink-receiving layer is opaque and has a poor gloss.

[0010] Various types of ink jet recording sheets having an ink-receivinglayer containing a resin capable of dissolving therein the ink and ofswelling by the ink are practically used. These types of ink jetrecording sheets have an enhanced gloss. However, they aredisadvantageous in that the resultant ink-receiving layer exhibits a lowink-drying rate and unsatisfactory resistance to moisture and water.

[0011] To enhance the smoothness and gloss of the ink-receiving layer,it has been attempted to form the ink-receiving layer in a two or morelayered structure wherein an uppermost layer has a high gloss. This typeof ink jet recording sheet is disclosed in, for example, JapaneseUnexamined Patent Publications No. 3-215,080, No. 3-256,785, No.7-89,220, 7-101,142 and 7-117,335. In this type of ink jet recordingsheet, colloidal particles or a complex of colloidal particles arecommonly used as a principal component of the high gloss layer. Thistype of high gloss layer is formed from the colloidal particles orcomplex thereof dispersed in a binder comprising a polymer latex, toestablish a satisfactory transparency and ink-absorption. When thepolymer latex is used as a binder, a plurality of small cracks areformed in the resultant coating layer. The small cracks are contributoryto enhancing the ink-absorption of the ink-receiving layer. However, thesmall cracks cause the resultant ink dots formed on the crackedink-receiving layer to have jagged circumferences significantlydifferent from round circumferences, and thus the resultant ink imagesto exhibit reduced clarity and sharpness. Also, the small cracks causethe printed ink to spread on the ink-receiving layer and thus the inkdots to be enlarged. When the ink dots are formed in a usual density ofthe level of 360 dots per inch×360 dots per inch (dpi), the spread ofthe ink dots due to the small cracks of the ink-receiving layer does notcause any problems. However, if the ink dots are formed in a highdensity of the level of 720 dots per inch×720 dots per inch or more, thespread of the ink causes the spread ink dots to be connected to eachother and thus the resultant ink images exhibits significantly reducedclarity and sharpness. Also, the colloidal particles in the uppermosthigh-gloss layer are primary particles and thus have substantially nofine pores capable of receiving the ink therein. Therefore, the ink isabsorbed in the ink-fixing layer formed under the uppermost high-glosslayer. In the above-mentioned multi-layered ink-receiving layer, anink-fixing layer is formed under the high gloss layer, and the thicknessof the ink-fixing layer is larger than that of the high gloss layer.Also, the ink-fixing layer contains secondary particles of a pigmenthaving a particle size in a μm order, the resultant multi-layeredink-receiving layer exhibits a significantly reduced transparency andthus the ink images fixed in the ink-receiving layer exhibit anunsatisfactory color density. Especially, this type of ink-receivinglayer exhibits a reduced light reflection and thus an insufficientgloss.

[0012] To prevent the formation of the small cracks in the ink-receivinglayer, Japanese Unexamined Patent Publication No. 7-117,334 provides anink-receiving layer formed from a composition comprising pigmentparticles with a particle size of 0.1 μm or less and a polyvinyl alcoholwith a degree of polymerization of 4,000 or more. The pigment particlesare selected from primary pigment particles for example, colloidalsilica or alumina sol. Therefore, in the resultant ink-receiving layer,the ink absorption and the transparency are unbalanced. Namely, sincethe pigment primary particles per se have no ink-absorption, the ink isabsorbed in the gaps between the pigment primary particles. The gapsbetween the pigment primary particles in the ink-receiving layer arefilled by a film-forming binder which is necessary to bond the pigmentparticles and to form an ink receiving layer. Therefore, thebinder-filled gaps between the pigment particles exhibit a low inkabsorption. To completely absorb a large amount of the ink, theink-receiving layer must be formed in a large thickness. Theink-receiving layer with a large thickness easily forms small cracks.Also, to obtain an ink-receiving layer having a high transparency, thepigment primary particles must be selected from those having a smallparticle size.

[0013] The smaller the pigment primary particle size, the lower theink-absorbing rate of the resultant ink-receiving layer. However, thelarger the pigment primary particle size, the lower the transparency ofthe resultant ink-receiving layer, and the lower the color density ofthe printed ink images.

[0014] Japanese Unexamined Patent Publication No. 2-276,670 discloses anink-receiving layer for an ink jet recording material. The ink-receivinglayer is formed from a mixture of pseudoboehmite and a binder and has aplurality of pores having a radius of 40 to 100 angstrom (4 to 10 nm)and a total volume of 0.1 to 0.4 ml/g. The pseudoboehmite particlesaffect the hue of a certain type of inks which are affected by alumina.Accordingly, the pseudoboehmite-containing ink-receiving layer isunsuitable for the above-mentioned inks, for example, Acid Red 52 (foodred dye No. 106). Also, the pseudoboehmite has a disadvantage in that itper se is yellowed with a lapse of time. Further, the pseudoboehmite isexpensive and thus is difficult to use in practice. Furthermore, thepseudoboehmite particles are colloidal primary particles having a poorink absorption and thus the resultant ink-receiving layer has aninsufficient total pore volume and exhibits an unsatisfactoryink-absorbing rate and ink-absorption capacity.

[0015] Japanese Unexamined Patent Publications No. 5-32,037 and No.6-199,034 disclose an ink jet recording material having an ink-receivinglayer which contains agglomerated secondary particles of pseudoboehmitewith a particle size of 100 to 500 nm and is provided with pores havinga radius controlled to 30 to 100 angstrom (3 to 10 nm). However, thisink-receiving layer contains the pseudoboehmite particles and thus cannot be released from the disadvantages derived from the pseudoboehmiteparticles. Namely, although the agglomerated secondary particles ofpseudoboehmite are contributory to enhance the ink absorption of theresultant ink-receiving layer to a certain extent, the total pore volumeof the ink-receiving layer containing the agglomerated secondaryparticles of pseudoboehmite is not sufficiently large and thus when theink dots are formed in a high density of 720 dip×720 dpi or more, theink-receiving layer does not completely absorb the ink at a satisfactoryink-absorbing rate.

[0016] Japanese Unexamined Patent Publication No. 7-117,335 discloses anink jet recording material having an ink-receiving layer having highsmoothness and gloss. This ink-receiving layer is formed in amulti-layered structure and has an uppermost gloss layer comprising, asa principal component, colloidal particles or composite colloidalparticles, and laminated on an ink-fixing layer. The uppermost glosslayer is formed by pressing the uppermost layer in a wetted conditionagainst a mirror-finished perperal surface of a shaping roll. However,the uppermost layer laminated on the ink-fixing layer easily sinks intothe ink-fixing layer upon pressing and thus is difficult to sufficientlysmooth by the mirror surface-transfer method. Accordingly, to enhancethe mirror surface-transfer effect onto the uppermost layer, a polymerlatex is used as a binder for the formation of the uppermost glosslayer. The use of the polymer latex causes the resultant uppermost glosslayer to be easily and finely cracked. The fine cracks contribute toenhancing the ink absorption rate in the uppermost gloss layer. However,the fine cracks also cause the resultant uppermost gloss layer toexhibit a reduced gloss and the ink dots formed on the uppermost glosslayer to have jagged circumferences and to be easily connected to eachother. These features of the ink dots result in reduced clarity andsharpness of the printed ink images.

[0017] Further, in the above-mentioned ink jet recording material, sincethe uppermost layer of the ink-receiving layer is smoothed by amirror-finished surface, and then dried, the substrate must be anair-permeable sheet, for example, a paper sheet. A non-permeable, highsmoothness sheet, for example, a plastic film or a laminate, cannot beused as the substrate. When a paper sheet having a rough surface is usedas a substrate, the resultant ink-receiving layer has a rough surfacederived from the paper sheet surface. Also, when the recording sheet isdried water vapor permeates through the ink-receiving layer and formspinholes in the ink-receiving layer. Therefore, the ink-receiving layerhaving a high gloss similar to that of photographic printing sheets isdifficult to obtain.

[0018] To solve the above-mentioned problems, the inventors of thepresent invention have provided an ink jet recording material producedby forming an ink-receiving layer on a surface of a shaping base;bonding a substrate to the ink-receiving layer formed on the shapingbase through an intermediate layer comprising a bonding material or anadhesive material; and separating the resultant laminate from theshaping base. In this type of ink jet recording material, awater-soluble resin can be used as a binder of the ink-receiving layer,the resultant ink dots on the ink-receiving layer is in the form of atrue circle and the ink-receiving layer exhibits a high smoothness, ahigh ink absorption and a high gloss.

[0019] However, where the ink-receiving layer is formed in two ormore-layered structure on the shaping base surface, a first layer(corresponding to an porous uppermost layer of the resultant ink jetrecording is formed on the sheet) shaping base surface and then second,third and other layers are successively formed on the porous uppermostlayer. In this case, pores or voids may be formed in the surfaceportions of the second, third or other layers, and may be retained evenafter the resultant multi-layered ink-receiving layer is transferredfrom the shaping base to the substrate surface. Also, when the coatingliquids for the second, third and other layers are successively coatedon the uppermost layer, the binder contained in those layers may diffuseinto the first layer (porous uppermost layer) so as to change theink-absorbing property of the first layer (porous uppermost layer).Further, as the amounts of the second, third and other layers areincreased, the resultant multi-layered ink-receiving layer may exhibit apoor resistance to crack-formation.

[0020] U.S. Pat. No. 5,612,281 for Kobayashi et al discloses a recordingsheet for ink jet recording having a transparent support and transparentcolorant-receptive layer having a three dimensional network structureformed from silicic anhydride particles and a water-soluble resin. Thecoating solution for the colorant-receptive layer is prepared by, forexample, by adding silica fine particles having an average primaryparticle size (diameter) of not more than 10 nm to water, dispersing thefine silica particles by using a high speed rotary wet colloid mill,adding, to the resultant aqueous fine silica dispersion, an aqueouspolyvinyl alcohol solution and adjusting the pH of the resultant aqueousdispersion to 4.5, to obtain a homogeneous sol. The coating solution iscoated on the transparent support and dried to provide thecolorant-receptive layer. When the coating solution layer is dried onthe transparent support and reaches a gelation concentration through theevaporation of water, a wet gel is formed and, as the drying furtherprogresses, a porous xerogel is formed to obtain a colorant receptivelayer. In the resultant colorant receptive layer, the fine silicaanhydride particles having a primary particle size of not more than 10nm are adhered to each other through the polyvinyl alcohol binder toform a network structure, but not secondary particles each consisting ofa plurality of primary particles agglomerated with each other, of thefine silica particles. Thus, the colorant receptive layer has arelatively high density and exhibits a poor ink absorbing property. Thesilica really disclosed in the U.S. patent is only dry method silica(dry process silica). The dry method silica causes the resultantink-receiving layer to exhibit an ink absorbing property lower than thatof the wet method silica (wet process silica).

SUMMARY OF THE INVENTION

[0021] An object of the present invention is to provide an ink jetrecording material having a high gloss, a high resistance to weatheringand a high resistance to water and capable of recording ink imageshaving excellent clarity, and sharpness and satisfactory color density,brightness and brilliancy.

[0022] The above-mentioned object can be attained by the ink jetrecording material of the present invention which comprises:

[0023] a substrate; and

[0024] an ink-receiving layer formed on at least one surface of thesubstrate, wherein said ink-receiving layer comprises a binder, and aplurality of secondary particles, wherein said secondary particles havean average secondary particle size of 10 to 300 nm, each of saidsecondary particles consisting essentially of a plurality of primaryparticles of at least one member selected from the group consisting ofsilica prepared by wet method, which silica will be referred to as wetmethod silica hereinafter, and aluminosilicate, and wherein said primaryparticles are agglomerated with each other to form said secondaryparticles without any binder, in each of the secondary particles, poresbeing formed between the agglomerated primary particles.

[0025] In an embodiment of the ink jet recording material of the presentinvention, the ink-receiving layer has a haze value of 4 to 65%.

[0026] In another embodiment of the ink jet recording material of thepresent invention, the ink-receiving layer has a plurality of poresformed therein and exhibits a pore radius distribution curve having apeak corresponding to a pore radius of about 40 nm or less.

[0027] The process of the present invention for producing the ink jetrecording material comprises the steps of:

[0028] forming an ink-receiving layer comprising a binder, and aplurality of secondary particles, having an average secondary particlesize of 500 nm or less and each comprising a plurality of primaryparticles of at least one member selected from the group consisting ofsilica and aluminosilicate, and agglomerated with each other to form thesecondary particles, on a surface of a shaping base;

[0029] bonding the substrate to the ink-receiving layer provided on theshaping base to form a laminate; and

[0030] separating the resultant laminate from the shaping base.

BRIEF DESCRIPTION OF THE DRAWING

[0031]FIG. 1 is a graph showing a pore radius distribution curve and acumulative pore volume curve of all the pores, of the ink-receivinglayer of the ink jet recording sheet of Example 14 in accordance withthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] In the ink jet recording material of the present invention, anink-receiving layer is laminated on at least one surface of a substrate.The ink-receiving layer comprises a binder matrix and a plurality ofspecific pigment particles dispersed in the binder matrix. The specificpigment particles for the present invention are secondary particles eachcomprising a plurality of primary particles of at least one memberselected from the group consisting of silica and aluminosilicate, andagglomerated with each other to form the secondary particles having anaverage secondary particle size of 10 to 300 nm.

[0033] A conventional silica pigment is in the form of a powderconsisting of a plurality of particles having a particle size of severalμm, and thus exhibits a high ink absorption. However, this type ofconventional silica pigment causes a resultant coating layer to exhibita reduced transparency or to be opaque, and thus is unsuitable as apigment for an ink-receiving layer of an ink jet recording materialwhich is required to be capable of recording ink images having anenhanced color density and a high gloss. Also, the conventional silicapigment particles have a large particle size and thus the resultantink-receiving layer has a rough touch and is difficult to fully smooth.

[0034] The inventors of the present invention have studied to solve theabove-mentioned problems of the conventional silica pigment and foundthat the above-mentioned problems can be solved by using, as a pigment,secondary agglomeration particles comprising a plurality of primaryparticles of at least one member selected from silica andaluminosilicate, and agglomerated with each other to form the secondaryparticles which have an average secondary particle size controlled to 10to 300 nm, and is in the form of colloid particles, and as a preferablebinder, a water-soluble resin. The resultant ink-receiving layer is aporous layer having a satisfactory transparency and gloss and anenhanced ink-absorption. The silica is preferably an amorphous silica.

[0035] In the ink jet recording material of the present invention, sincethe specific colloidal particles of silica and/or aluminosilicatepigment are utilized, the resultant ink-receiving layer has an enhancedgloss and weathering resistance and capable of recording ink images withenhanced quality, in comparison with the conventional ink jet recordingmaterials in which a conventional alumina or boehmite pigment isemployed.

[0036] In the present invention, the pigment particles must be secondaryparticles each comprising an agglomeration of a plurality of primaryparticles of silica and/or aluminosilicate. Also, the secondaryparticles have an average particle size of 10 to 300 nm and are in theform of colloidal particles. If the conventional colloidal primaryparticles of silica and/or aluminosilicate are directly dispersed in thebinder matrix, the resultant ink-receiving layer has a relatively densestructure and exhibits a decreased transparency and a reduced inkabsorption. Therefore, to increase the ink-absorption, the ink-receivinglayer must be formed in an increased thickness. The thick ink-receivinglayer exhibits a low resistance to cracking. Also, the thickink-receiving layer can be formed by complicated coating procedures. Thesilica and/or aluminosilicate secondary particles may containnon-agglomerated primary particles thereof in a small amount, forexample, not exceeding 40% by weight.

[0037] The colloidal secondary particles of silica and/oraluminosilicate usable for the present invention have a poorself-bonding activity. Therefore, in the formation of the ink-receivinglayer, a binder for the colloidal secondary particles must be used.

[0038] In the ink jet recording material of the present invention, whena combination of the colloidal secondary particles with a binderpreferably comprising a water-soluble resin, for example, a polyvinylalcohol is used as a principal component, an ink-receiving layer havinga satisfactory transparency and a high gloss similar to that of thephotographic paper sheet can be obtained. Also, since the ink-receivinglayer is substantially transparent, the ink jet recording material ofthe present invention can be used for OHP.

[0039] Further, in the production of the ink jet recording sheet of thepresent invention, when the ink-receiving layer is formed on a smoothsurface of a shaping base, and transferred and bonded to a substrate andthen the resultant laminate is separated from the shaping base, theresultant ink-receiving layer has high smoothness and gloss.

[0040] The ink-receiving layer may be bonded to the substrate directlyor through a bonding or adhesive material layer.

[0041] The conventional colloidal silica pigment is a dispersion of aplurality of primary particles, and has a lower ink recording densityand ink absorption capacity than those of the specific secondaryparticles of silica usable for the present invention.

[0042] The substrate usable for the present invention comprises a memberselected from, for example, regenerated cellulose films (cellophane);plastic resin films, for example, polyethylene, polypropylene, softpolyvinyl chloride resin, hard polyvinyl chloride resin, and polyesterfilms; paper sheets, for example, wood-free paper sheets, art papersheets, coated paper sheets, cast-coated paper sheets, metallicfoil-laminated paper sheets, kraft paper sheets, polyethylenefilm-laminated paper sheets, resin-impregnated paper sheets,metal-deposited paper sheets, and water-soluble paper sheets; metallicfoils; and synthetic paper sheets.

[0043] To obtain an ink-receiving layer having an excellent gloss, thesubstrate is preferably formed from a water-impermeable plastic resinfilm or resin-laminated paper sheet. When the substrate is formed from atransparent plastic resin film, the resultant recording material is atransparent recording material and can be used for OHP.

[0044] As mentioned above, the pigment particles usable for theink-receiving layer of the present invention are secondary particlesformed from primary particles of a member selected from silica andaluminosilicate having a specific primary particle size of 3 to 40 nmand are agglomerated with each other. The secondary particles have asecondary particle size of 10 to 300 nm.

[0045] Generally, a colloidal solution contains a plurality of colloidalparticles having a particle size of about 1,000 nm or less and uniformlydispersed in a dispersion medium, for example, an aqueous medium.Accordingly, the silica or aluminosilicate secondary particles usablefor the present invention having a particle size of 10 to 300 nm are inthe form of colloidal particles. The silica or aluminosilicate secondaryparticles can be prepared by any conventional colloid forming method.For example, the secondary particles can be prepared by applying astrong mechanical stress to conventional synthetic amorphous silicaagglomerate particles having a particle size of, for example, 1 μm to 50μm, by using mechanical dividing means. Usually, the conventionalsynthetic amorphous silica agglomerate particles available in trade havea particle size of about 2 to 15 μm. This preparation method is referredto as a breaking down method wherein the synthetic amorphous silicaparticles are finely divided, while allowing the resultant primaryparticles to be agglomerated into secondary particles having an averagesecondary particle size of 10 to 300 nm.

[0046] The conventional synthetic amorphous silica agglomerate particleshaving a large particle size of 1 μm to 50 μm and usable for a breakingdown procedure can be produced by a wet method (wet process).

[0047] The typical method of producing silica particles will beillustrated below.

[0048] The methods of producing the amorphous silica are classified intowet methods (wet processes) and dry methods (dry processes). The wetmethod silica is produced by using, as a starting material, siliceoussand, mainly silicon dioxide, which exists in large amounts around theglobe. The physical properties of the amorphous silica can be controlledby the production method. Namely, various types of amorphous silicahaving a specific property necessary to desired use, for example,absorptive separations, catalyst carriers, and fillers for paints andresins, can be produced. The wet production methods of the amorphoussilica include gelatinization methods and precipitation methods.

[0049] In the gelation method, the amorphous silica is produced bymixing sodium silicate produced from a high purity siliceous sand withsulfuric acid to provide a silicic acid sol, gradually polymerizing thesilicic acid sol so as to form primary particles and thenthree-dimensionally to agglomerate the primary particles with each otherinto an agglomerate (secondary particles), namely to gelatinize the sol.By the above-mentioned method, the agglomerated particles of silica canbe prepared while using no binder. In the method, the amorphous silicaparticles having desired BET specific surface area in the range of from250 to 1500 m²/g can be produced by controlling the conditions forforming the primary particles. The resultant amorphous silica is finelydivided to a micrometer size.

[0050] In the precipitation methods, the amorphous silica is producedunder the same conditions as in the gelation method, except that thegrowth of the agglomerate (secondary) particles is stopped by influenceof reaction temperature, co-existing ions or surfactant, and theresultant agglomerate particles are allowed to precipitate. This type ofamorphous silica particles have a small BET specific surface area.Namely, the precipitated amorphous silica particle having a BET specificsurface area of 25 to 400 m²/g can be used for the present invention.

[0051] In the dry methods (or dry process), the amorphous silica isproduced by burning and hydrolysing SiCl₄ in gas phase. Therefore, thismethod is referred to as dry method against the wet method. In this drymethod, the resultant silica particles have no pores or inner gaps andno inner surface area and thus exhibit an ink absorbing property lowerthan that of the wet method silica particles.

[0052] The silica particles produced by the dry method have a very smallparticle size and form, in water, chained particles in which individualparticles are bonded with each other through hydrogen bonds. Thesehydrogen bonds are weak and thus are easily broken down when shearingforces are applied thereto.

[0053] The differences in the performance of the resultant amorphoussilica pigments between the amorphous silica pigment production methodsare as follows.

[0054] The amorphous silica pigment particles produced by the gelationmethod include primary particles having a small particle size and astrong agglomerating power and thus the resultant secondary particleshave a relatively dense structure.

[0055] In the amorphous silica pigment produced by the precipitationmethod, the primary particles have a large particle size, and a lowagglomeration power, and thus the resultant secondary particles may havea relatively loose structure. The fine pores are gaps formed between theprimary particles agglomerated with each other and thus the pore volumeis a controllable parameter of the agglomerate particles.

[0056] The amorphous silica primary particles made by the gelatinizationmethod form agglomerate (secondary) particles having a higher strengththan those produced by the precipitation method. The strong agglomerateparticles are expected to contribute to enhancing the strength of thecoating layer.

[0057] In the ink jet recording material, the agglomerated amorphoussilica particles produced by the wet method are preferably employed.These agglomerated amorphous silica particles can be pulverized by, forexample, the breaking down method, into secondary particles having thedesired secondary particle size.

[0058] In the wet method silica particles, a plurality of the primaryparticles are agglomerated with each other by attraction force betweenthe primary particles to form a secondary particles the attractionbetween the primary particles is due to a force including hydrogenbonding force between silanol groups located on the surfaces of theprimary particles and van der Waals force between the primary particles.

[0059] The aluminosilicate particles have an amorphous structure and canbe produced by subjecting a mixture containing, as principal components,an aluminum alkoxide and a silicon alkoxide to an hydrolysis procedure,and are a complex product comprising alumina moieties and silicamoieties which are closely combined with each other to such an extentthat these moieties cannot be isolated from each other. Usually, in thealuminosilicate particles, the alumina moieties (Al₂O₃) and the silicamoieties (SiO₂) are contained in a weight ratio of 1:4 to 4:1,preferably about 6:2. The aluminosilicate particles usable for thepresent invention may further contain an additional moiety, for example,titanium alkoxide, zinc alkoxide and calcium alkoxide, in an amount of10% by weight or less, preferably 0.1 to 2% by weight. These additionalmoiety-containing aluminosilicate particles can be produced by adding acorresponding metal alkoxide to the additional moiety to the aluminumalkoxide and silicon alkoxide.

[0060] The aluminosilicate particles are prepared in an alcoholicatmosphere, and the resultant particles are in the form of secondaryparticles having a particle size in the order of μm.

[0061] To reduce the aluminosilicate secondary particle size to 10 to300 nm, the above-mentioned aluminosilicate secondary particles suppliedfrom the preparation process are divided in a medium, for example, anaqueous medium, by a mechanical dividing means.

[0062] The mechanical dividing means for the silica and aluminosilicateparticles can be selected from, for example, ultrasonic homogenizers,high speed rotation mills, roller mills, container-driving medium mills,medium agitating mills, jet mills, mortar, grinders (in which a materialto be ground is placed in a bowl-shaped container and knead-ground witha pestle-shaped rod), and sand grinders.

[0063] The average primary and secondary particle sizes of the silicaand aluminosilicate particles can be determined by using an electronmicroscope (SEM or TEM). Namely, an electron microscopic photograph ofthe particles is taken at a magnification of 10,000 to 400,000, thesizes of the particles located in an area of 5 cm×5 cm in the photographare measured and an average of the measured particle sizes (martindiameter) is calculated.

[0064] In the present invention, the average size of the secondaryparticles of the silica or aluminosilicate is controlled to 10 to 300nm, preferably 10 to 200 nm, more preferably 10 to 150 nm, still morepreferably 20 to 100 nm.

[0065] If the silica or aluminosilicate secondary particles having anaverage particle size of more than 300 nm are used, the resultantink-receiving layer exhibits an unsatisfactory transparency, theresultant ink images exhibit an unsatisfactory color density and thus anexpected ink jet recording material having a high gloss after printingcannot be obtained. Also, if the average secondary particle size issmaller than 10 nm, the resultant ink-receiving layer exhibits anunsatisfactory ink absorption and ink-adsorbing rate.

[0066] In the present invention, the average size of the primaryparticles of silica and aluminosilicate is preferably controlled to 3 to40 nm, more preferably 3 to 30 nm, still more preferably 5 to 30 nm. Ifthe primary particle size is less than 3 nm, the resultant particles mayhave extremely small gaps between the primary particles and thus exhibita significantly low capacity for ink or ink solvent absorption. Also, ifthe average primary particle size is more than 40 nm, the resultantsecondary agglomeration particles may have too large a size and theresultant ink-receiving layer may exhibit an unsatisfactorytransparency. In the ink jet recording material of the presentinvention, the wet method silica exhibits a recording property-enhancingeffect higher rather than that of aluminosilicate.

[0067] Since the silica and aluminosilicate particles have a poorfilm-forming property, they must be bonded by using a binder to form theink-receiving layer. The binder comprises a water-soluble resin or anaqueous emulsion, a latex, or a dispersion of resin. The water-solubleresin is preferably selected from polyvinyl alcohol (PVA), water-solublemodified polyvinyl alcohols, for example, silanol-modified polyvinylalcohols, and cation-modified polyvinyl alcohols, polyvinyl pyrrolidonecasein, soybean protein, synthetic proteins, starch, and water-solublecellulose derivatives, for example, carboxy-methylcellulose andmethylcellulose.

[0068] The binder may be an aqueous emulsion, latex or dispersion of awater-insoluble conjugated diene polymer selected from, for example,styrene-butadiene copolymers, and methyl methacrylate-butadienecopolymers. However, a water soluble resin is preferably used as abinder because the resultant ink receiving layer exhibits a high inkabsorption.

[0069] From the view point of dispersibility and coating liquidstability, the polyvinyl alcohol is most preferable for the binder.Especially, the water-soluble resin contributory to enhancing the inkabsorption of the ink-receiving layer is selected from polyvinyl alcoholhaving a degree of polymerization of 2,000 or more, more preferably2,000 to 5,000. To form an ink-receiving layer having an enhanced waterresistance, the polyvinyl alcohol is preferably selected from thosehaving a degree of saponification of 95% or more, more preferably, 97%to 100%.

[0070] In the ink-receiving layer of the present invention, there is nolimitation to the solid weight ratio of the binder to the silica and/oraluminosilicate pigment particles. Preferably, the binder/pigment ratiois 10:1 to 10:10, more preferably 10:2 to 10:6. If the content of thebinder is too high, the resultant ink-receiving layer has a small totalvolume of pores and thus exhibits an unsatisfactory ink absorption.Also, if the content of the binder is too small, the resultantink-receiving layer has an unsatisfactory resistance to cracking and toolow a mechanical strength.

[0071] The ink-receiving layer of the present invention optionallycontains, in addition to the specific silica and/or aluminosilicateparticles and the binder, an additional pigment selected fromconventional inorganic and organic pigments for example, colloidalsilica in the form of primary particles, kaolin, clay, calcined clay,zinc oxide, tin oxide, magnesium sulfate, aluminum oxide, aluminumhydroxide, calcium carbonate, satin white, aluminum silicate, smectites,zeolites, magnesium silicate, magnesium carbonate, magnesium oxide,diatomaceous earth, thermoplastic resin pigments, for example, styrenepolymer pigments and thermosetting resin pigments, for example,urea-formaldehyde resin and benzoguanamine resin pigments. However, tomaintain the smoothness and ink absorption of the ink-receiving layer ata satisfactory level, the content of the additional pigment ispreferably restricted to a level of not exceeding 20% by weight based onthe weight of the specific silica and/or aluminosilicate particles.Also, for the purpose of enabling the ink-receiving layer to exhibit asatisfactory transparency, the particle size of the additional pigmentis preferably 2 μm or less.

[0072] In the ink-receiving layer of the present invention, a cationicresin is optionally further contained to enhance the ink-fixing propertyof the ink-receiving layer. The cationic resin usable for the purpose ispreferably selected from polyalkylenepolyamine resins, for example,polyethylenepolyamine and polypropylenepolyamine resins and modifiedpolyalkylenepolyamine resins, modified polyacrylic resins with atertiary amine group or quaternary ammonium group, and diacrylamineresins. Usually, the cationic resin is contained preferably in an amountof 1 to 30 parts by weight, more preferably 5 to 20 parts by weight, per100 parts of the total weight of the pigment component. Also, theink-receiving layer optionally contains an additive selected fromconventional dispersing agents, thickening agent, antifoaming agents,coloring materials, antistatic agents and antiseptic agents.

[0073] There is no specific limitation to the amount of the inkreceiving layer.

[0074] The ink-receiving layer of the present invention is providedpreferably in a coating amount of 1 to 100 g/m², more preferably 5 to 60g/m². If the coating amount of the ink-receiving layer is too small, theincreasing layer is difficult to form with a satisfactory uniformity.Also, if the coating amount is more than 100 g/m², the performance andeffect of the resultant ink-receiving layer are saturated and sometimesthe ink-receiving layer exhibits a reduced resistance to cracking. Athick ink-receiving layer having a weight of 15 g/m² or more can beobtained by increasing the viscosity of the coating liquid and/or thetotal concentration of the solid contents in the coating liquid for theink-receiving layer, or by repeatedly coating the coating liquid twotimes or more.

[0075] In a preferred embodiment of the ink jet recording material ofthe present invention, the image-receiving layer containing the specificsilica and/or aluminosilicate secondary particle have a plurality ofpores formed therein due to the specific secondary particles andexhibits a pore radius distribution curve in which a peak appears at apore radius of 40 nm or less.

[0076] Namely, in this preferable embodiment of the present invention,an ink-receiving layer formed on a surface of a substrate comprises abinder matrix comprising a binder, preferably a water-soluble resin, anda plurality of secondary particles having an average secondary particlesize of 10 to 300 nm, preferably 10 to 150 nm, dispersed in the bindermatrix, and each comprising a plurality of primary particles of at leastone member selected from silica and aluminosilicate, having an averageprimary particle size of 3 to 40 nm and agglomerated with each other toform the secondary particles, has a plurality of pores formed therein,and exhibits a pore radius distribution curve having a peakcorresponding to a pore radius of about 40 nm or less.

[0077] The above-mentioned secondary particles preferably have a totalpore volume of 0.1 ml/g or more, more preferably 0.5 ml/g or more.

[0078] When the ink-receiving layer is formed by coating a surface ofthe substrate with a coating liquid containing the specific silica andaluminosilicate secondary particles, sometimes a small number of airbubbles are included in the resultant ink-receiving layer. Also, due toa scattering of the measurement data of the pore radius in a pore radiustester, the resultant pore radius distribution curve sometimes has apeak corresponding to a pore radius of more than 40 nm. However, thispeak is smaller than the peak appearing at a pore radius of 40 nm orless. Also, in the pore radius distribution curve of the image-receivinglayer, a region corresponding to a pore radius of 6 μm or more may havea small peak.

[0079] However, in the pore radius distribution curve of theink-receiving layer of the present invention, the peak appears in theregion corresponding to a pore radius of 40 nm or less and substantiallyno peak appears in the region corresponding to a pore radius of morethan 40 nm but not more than 6 μm. Usually, there is no lower limit tothe pore radius at which a peak appears in the pore radius distributioncurve. The peak may appear at a very small pore radius of about 1 nm.

[0080] The total volume of the pores having a pore radius of 40 nm orless corresponds preferably to 40% or more, more preferably 65% or more,of the total volume of all the pores. In the present invention, theabove-mentioned peak appearing in the pore radius distribution curve hasa height corresponding to about 10% or more of the height of the highestpeak appearing in the pore radius distribution. Smaller peaks sometimesappear due to the scattering of the measurement data and thus areusually neglected.

[0081] When the pores included in the ink-receiving layer have theabove-defined pore radius distribution curve, the resultant porousink-receiving layer has a high gloss, and satisfactory transparency,ink-absorbing rate and ink-absorption capacity, and can receive truecircle-shaped ink dots. Also, in the present invention, the recorded inkimages recorded in the ink-receiving layer has a high color density andbrightness, and the resultant ink-receiving layer has an enhancedweathering resistance and a high ink-absorbing rate.

[0082] The silica or aluminosilicate particles for the present inventionmust be colloidal particles consisting essentially of secondaryparticles each composed of a plurality of primary particles agglomeratedwith each other. When the ink is absorbed in the pores formed betweenthe secondary particles and having a relatively large pore size, the inkis further absorbed in the fine pores formed between the primaryparticles in the secondary particles and having a relatively small poresize, and thus the ink receiving layer exhibiting enhanced ink absorbingrate, and ink absorption capacity can be obtained.

[0083] When colloidal particles consisting of primary particles simplydispersed, for example, colloidal silica particles from the trade, areused, the resultant ink receiving layer formed by coating a substratewith a coating composition containing the colloidal particles has arelatively high density, and the ink can be absorbed only in the poresformed between the primary particles. Therefore, to increase the inkabsorbing rate and the ink absorption capacity, primary particles havinga large particle size must be used. The increase in the particle sizecauses the transparency of the resultant ink receiving layer to bereduced. Also, to provide an ink receiving layer having a high inkabsorbing property, the ink receiving layer must be formed in a highcoating amount. The high coating amount causes the resultant inkreceiving layer to exhibit a reduced resistance to cracking and thecoating procedure to be complicated.

[0084] The pigment particles used for the present invention may containa small amount of primary particles not agglomerated with each other.

[0085] In the ink jet recording material of the present invention,preferably the ink receiving layer includes a plurality of pores formedtherein, the total volume of all the pores is 0.6 ml/g or more, morepreferably 1 ml/g or more, and the total volume of the pores with a poresize of 3 to 20 nm is 0.3 ml/g or more, preferably 0.4 ml/g or more.This preferable ink receiving layer has enhanced transparency,ink-absorbing rate and ink-absorption capacity and the recorded inkimages have enhanced color density and gloss.

[0086] There is no upper limit to the total volume of all the pores inthe ink-receiving layer. Usually, the total volume of all the pores canbe increased up to about 2.5 ml/g. Also, there is no upper limit to thetotal volume of the pores with a pore size of 3 to 20 nm. Usually, thetotal volume of the pores may be 2.0 ml/g or more. Preferably the totalvolume of the pores with a pore size of 3 to 20 nm is 0.4 to 1.5 ml/g.

[0087] Since this type ink-receiving layer is entirely transparent, whena transparent substrate sheet is used, the resultant ink jet recordingmaterial can be used for OHP. The smoothness and gloss of theink-receiving layer can be improved by forming a coating layercorresponding to the ink-receiving layer on a smooth surface of ashaping base, bonding a substrate to the coating layer, and thenseparating a resultant laminate from the shaping base.

[0088] The pore radius distribution of the ink-receiving layer can bedetermined by the following measurement. An ink-receiving layer isformed on a surface of a thermoplastic film, and then removed from thethermoplastic film by using a peeling tool, for example, a cutter knife.If the thermoplastic film has substantially no influence on themeasurement of the pore radius distribution, the film may not beseparated from the ink-receiving layer.

[0089] The measurement specimen is subjected to a cumulative pore volumemeasurement by a mercury-forcing method using a micrometrix poresizer9320 (trademark, made by Shimazu Seisakusho). A pore radius distributionis calculated from the cumulative pore volume test result. The pore sizeis calculated from the following equation, on the assumption that thecross-sections of the pores are circle-shaped.

R=−2γ cos θ/P

[0090] wherein R represents a radius of pore, γ represent a surfacetension of mercury, θ represent a contact angle of mercury, and Prepresents a mercury-forcing pressure.

[0091] In the measurement, the surface tension of mercury is 482.536dye/cm and the contact angle is 130 degrees, the mercury-forcingpressure is 0 to 30 psia in a low pressure region for a pore radius tobe measured of 180 to 3 μm, and 0 to 30,000 psia in a high pressureregion for a pore radius to be measured of 3 μm to 3 nm.

[0092] The cumulative pore volume of the ink-receiving layer specimencan be calculated from the weight of the specimen and the cumulativepore volume curve.

[0093] In another preferable embodiment of the ink jet recordingmaterial of the present invention, the ink-receiving layer contains thespecific silica and/or aluminosilicate secondary particles having anaverage secondary particle size of 10 to 300 nm, preferably 10 to 200 nmand has a haze value of 4 to 65% preferably 4 to 55%, more preferably 4to 35%, still more preferably 4 to 20%. This type of ink-receiving layerexhibits an enhanced ink-absorbing rate, ink-absorption capacity, glossand transparency and the resultant ink dots recorded thereon aretrue-circle-shaped.

[0094] The haze value of the ink-receiving layer is measured by thefollowing method.

[0095] An ink-receiving layer is coated on a transparent thermoplasticfilm having a thickness of 75 μm (trademark: Lumiler T, made by TorayIndustries, Inc.), and subjected to a haze value measurement using ahaze meter (reflection and transmission tester, Model: HR-100, made byMurakami Shikisaigijutsu Kenkyusho). The measurement is carried out inaccordance with JIS K7105 as follows.

[0096] (1) A standard white plate is fixed to the tester and an amountof incident light is controlled so that an indicator of the testerindicates a value Ti of 100.

[0097] (2) A specimen is fixed together with the standard white plate,and a total amount T₂ of light transmitted through the specimen ismeasured.

[0098] (3) The standard white plate and specimen are removed, a lighttrap is fixed, and an amount T₃ of light scattered in the tester ismeasured.

[0099] (4) The specimen is attached together with the light trap to thetester, and an amount T₄ of scattered light by the tester and thespecimen is measured.

[0100] (5) Then the haze value of the specimen is calculated inaccordance with the following equations.

Total light transmission Tt(%)=(T₂/T₁)×100

Defused light transmission Td(%)={[T₄−T₃(T₂/T₁)]/T₁}×100

Haze value H(%)=(Td/Tt)×100

[0101] If the haze value is less than 4%, although the resultantink-receiving layer may exhibit an enhanced transparency, theink-absorbing rate and ink-absorption capacity of the ink-receivinglayer may be unsatisfactory. Also, if the haze value is more than 65%,the resultant ink-receiving layer may exhibit too low a transparency andthe recorded ink images may have an unsatisfactory color density. Thehaze value is preferably 4 to 35%, more preferably 4 to 20%. The hazevalue of the ink-receiving layer is variable depending not only on thesecondary particle size but also on the primary particle size of thesilica and/or aluminosilicate colloidal particles. Preferred averagesecondary particle size is 10 to 200 nm and the preferred averageprimary particle size is 3 to 40 nm. Also, the haze value of theink-receiving layer is variable depending on the amount and refractiveindex of the binder. Namely, a gloss ink-receiving layer having a lowhaze value (a high transparency) can be obtained by using a binderhaving a high transparency.

[0102] Also, even when the ink-receiving layer is formed in an amount of10 g/m² or more, the color density and gloss of the printed ink imagescan be enhanced by adjusting the haze value of the ink-receiving layerto 4 to 65%, and the resultant ink jet recording material can recordthereon high quantity ink images.

[0103] In still another preferable embodiment of the ink jet recordingmaterial of the present invention, the surface of the ink-receivinglayer has a Bekk smoothness of 1,000 seconds to record thereon inkimages with a high gloss.

[0104] The ink jet recording material of the present inventionoptionally further comprises at least one additional ink-absorbent layercomprising a binder resin and a plurality of pigment particles. Theadditional ink-absorbent layer is laminated preferably between thesubstrate and the ink-receiving layer. Namely, in this case, theink-receiving layer forms an actual uppermost (or outermost) layer andthe additional ink-absorbent layer forms an actual inside layer of theink jet recording material of the present invention.

[0105] The additional ink-absorbent layer may be the same as ordifferent from the ink-receiving layer in the composition thereof.

[0106] Where the additional ink-absorbent layer contains, as a pigmentcomponent, the same specific silica and/or aluminosilicate secondaryparticles as those of the ink-receiving layer, the resultant ink jetrecording material has most satisfactory gloss and transparency and canrecord thereon ink images having most satisfactory color density,clarity and brightness.

[0107] Nevertheless, a combination of the ink-absorbing layer with atleast one additional ink-absorbent layer containing a pigment differentfrom the specific silica and/or aluminosilicate secondary particles canexhibit a satisfactory ink-absorbing rate, ink-absorption capacity,gloss, transparency, water-resistance and whethering resistance and canrecord thereon ink images with satisfactory color density, clarity andbrightness.

[0108] To ensure the high gloss of the ink receiving layer afterprinting, the amount of the specific silica and/or aluminosilicatesecondary particle-containing layer is preferably controlled to a levelof 50 to 100% by weight based on the total weight of the ink-receivinglayer and the additional ink-absorbent layer. Even if the amount of thesilica and/or aluminosilicate secondary particle-containing layer isless than 50%, the resultant ink jet recording material can exhibit acertain gloss but cannot exhibit a high gloss and brightness similar tothose of photographic paper sheets.

[0109] When the amount of the specific silica and/or aluminosilicatesecondary particle-containing layer is 50 to 100% based on the totalweight of the ink-receiving layer and the additional ink-absorbentlayer, the resultant gloss and brightness are similar to those of theconventional photographic paper sheets.

[0110] As mentioned above, the additional ink-absorbent layer ispreferably located between the substrate and the ink-receiving layer,and comprises a plurality of pigment particles which are conventionallyused for the coated paper production and have an average particle sizeof 0.5 μm or more. The pigment for the additional ink-absorbent layer ispreferably selected from synthetic amorphous silica, clay, alumina, orsmectite particles. The synthetic amorphous silica pigment is mostpreferable for recording ink images having satisfactory color density,clarity and brightness.

[0111] The additional ink-absorbent layer may comprise theabove-mentioned specific agglomerate particles of silica and/oraluminosilicate usable for the ink receiving layer.

[0112] In the additional ink-absorbent layer, the binder comprises, forexample, a water-soluble resin, for example, polyvinyl alcohols, caseinand starches as mentioned above, and a latex or aqueous emulsion ordispersion of a water-insoluble synthetic resin, for example, astyrene-butadiene copolymer later. Preferably the water-soluble resin isused.

[0113] The binder is contained preferably in an amount of 5 to 150 partsby weight, more preferably 10 to 50 parts by weight, per 100 parts bytotal weight of the pigment component. Also, the additionalink-absorbent layer optionally contains the cationic resin as mentionedabove, to enhance the ink-fixing property thereof. The cationic resin iscontained in an amount of preferably 1 to 30 parts by weight, morepreferably 5 to 20 parts by weight, per 100 parts by total weight of thepigment component. Further, the additional ink-absorbent layeroptionally contains an additive selected from dispersing agents,thickening agents, antifoaming agent, coloring materials, antistaticagents and antiseptic agents which are commonly used for the coatedpaper production, in a small amount, for example, 0.01 to 5 parts byweight per 100 parts by weight of the pigment component.

[0114] There is no limitation to the amount of the additionalink-absorbent layer. Usually, the amount of the additional ink-absorbentlayer is preferably adjusted to 3 to 30 g/m². If the amount is toosmall, the resultant additional ink-absorbent layer has too low anink-absorption capacity and thus is meaningless. Also, if the amount istoo large, the effect of the additional ink-absorbent layer is saturatedand sometimes results in an economical disadvantage.

[0115] Even when the ink-receiving layer is formed on the additionalink-absorbent layer, the ink receiving layer preferably has a haze valueof 4 to 65%, more preferably 4 to 55%, still more preferably 4 to 35%,further preferably 4 to 20%. Also, the additional ink-absorbent layermay comprise the specific silica and/or aluminosilicate secondaryparticles. To enhance the color density of the printed ink images,preferably, the average secondary particle size of the specific silicaand/or aluminosilicate secondary particles in the ink receiving layer issmaller than the particle size of the pigment component in theadditional ink-absorbent layer.

[0116] The ink-receiving layer and the additional ink-absorbent layercan be formed on the substrate by using a conventional coating methodand apparatus, for example, a die coater, a blade coater, air knifecoater, roll coater, bar coater, gravure coater, rod blade coater, lipcoater, curtain coater.

[0117] In still another preferable embodiment of the ink jet recordingmaterial of the present invention, the substrate is transparent. In thisembodiment, the ink-receiving layer preferably comprises the specificsilica and/or aluminosilicate secondary particles having a secondaryparticle size of 10 to 300 nm, preferably 10 to 200 nm, and preferably aprimary particle size of 3 to 40 nm, and has a haze value of 4 to 65%,more preferably 4 to 55%, still more preferably 4 to 35%, furtherpreferably 4 to 20%.

[0118] The transparent substrate can be formed from transparentpolymeric sheets or films, for example, regenerated cellulose films(cellophane), and thermoplastic films such as polyethylene,polypropylene, soft polyvinyl chloride resin, hard polyvinyl chlorideresin, polyester (polyethylene terephthalate, etc.) films. Thetransparent substrate preferably has a haze value of 20% or less.

[0119] Further preferably, the ink-receiving layer contains the specificsilica and/or aluminosilicate colloidal particles having an averageprimary particle size of 3 to 30 nm and an average secondary particlesize of 10 to 100 nm more preferably 20 to 80 nm, and has, as a whole, ahaze value of 20% or less. The haze value of the ink jet recordingmaterial can be determined in accordance with the measurement methodmentioned above.

[0120] The above-mentioned type of ink jet recording material of thepresent invention exhibits high transparency, ink-absorbing property,water resistance, whethering resistance, can record thereon ink imageswith high color density and clarity, and thus is useful as a transparentink jet recording sheet for, for example, OHP. If the haze value is morethan 20%, the resultant ink jet recording sheet is not suitable for OHP,because in this case, the projected images from the ink jet recordingsheet onto OHP may be unclear.

[0121] There is no lower limit to the haze value. The haze value may besmall, for example, 5% or less.

[0122] When an ink jet recording material having a haze value of 20% orless is designed, the primary and secondary particle sizes of the silicaand/or aluminosilicate particles should be controlled to the specificvalues as defined in the present invention. If the average primaryand/or secondary particle size is too small, the resultant ink-receivinglayer may exhibit an unsatisfactory ink-absorption property. In thiscase, to enhance the ink-absorption property, the thickness of theink-receiving layer must be undesirably increased. The thickink-receiving layer exhibits a reduced resistance to cracking.

[0123] In the ink jet recording material of the present invention, theink-receiving layer and optionally the additional ink-absorbent layercan be directly formed on a surface of the substrate by using a coatingapparatus. Alternatively, in another process for producing the ink jetrecording material of the present invention, the ink receiving layer isformed on a surface, especially a smoothed surface, of a shaping base; asubstrate is bounded to the ink-receiving layer on the shaping base; andthen the resultant laminate is separated from the shaping base surface.The resultant ink-receiving layer surface has an enhanced smoothness andgloss. The ink receiving layer on the shaping base may be bonded to thesubstrate through an intermediate layer comprising a bonding material oran adhesive material. The intermediate layer may be formed on a surfaceof the substrate and then the substrate surface may be bonded to theink-receiving layer on the shaping base surface through the intermediatelayer. Otherwise, the intermediate layer may be formed on theink-receiving layer on the shaping base and then the substrate is bondedto the intermediate layer.

[0124] The above-mentioned method using the smooth shaping base isespecially advantageous in that the resultant ink-receiving layercontaining the specific silica and/or aluminosilicate secondaryparticles can exhibit enhanced smoothness and gloss.

[0125] The bonding of the ink-receiving layer formed on the shaping basesurface to the substrate is preferably carried out by a conventionallaminating method, for example, dry laminating method, wet laminatingmethod, hot melt laminating method or extrusion laminating method.

[0126] In the wet, dry and hot melt laminating methods, preferably, anintermediate layer comprising a bonding or adhesive material is formedon a surface of the substrate, and then the intermediate layer on thesubstrate is superposed on the ink-receiving layer formed on the shapingbase, they are bonded under pressure, and then the resultant laminate isseparated from the shaping base to obtain an ink jet recording material.

[0127] In the extrusion laminating method, a melt of a thermoplasticresin, for example, a polyethylene resin melted at a temperature of 280to 320° C., is prepared in a melt-extruder and then extruded through afilm-forming slit onto a surface of a substrate to form an intermediatelayer; the ink receiving layer formed on the shaping base is superposedon the intermediate layer on the substrate; they are bonded to eachother under pressure while cooling by a cooling roll, and then theresultant laminate is removed from the shaping base.

[0128] When a pressure-sensitive adhesive is used for the intermediatelayer, a surface of the substrate is coated with the pressure-sensitiveadhesive by a conventional coating method, for example, bar coater, rollcoater or lip coater; the coated adhesive layer is dried; the driedadhesive layer is laminated on the ink-receiving layer formed on theshaping base; and then the resultant laminate is removed from theshaping base to obtain a ink jet recording material.

[0129] There is no specific limitation to the amount of the intermediatelayer as long as the resultant intermediate layer can firmly bond theink-receiving layer to the substrate therethrough. Usually, theintermediate layer formed from a thermoplastic resin, bonding materialor pressure-sensitive adhesive is preferably in an amount of 2 to 50g/m². If the amount of the intermediate layer is too small, the bondingstrength of the substrate to the ink-receiving layer may beunsatisfactory. Also, the intermediate layer is formed in too large anamount, the bonding strength may be saturated and an economicaldisadvantage may occur.

[0130] The intermediate layer for bonding the ink-receiving layer to thesubstrate can be formed from a member selected from thermoplasticpolymers, for example, ethyl cellulose, vinyl acetate polymer,copolymers and derivatives thereof, polyethylene, ethylene-vinyl acetatecopolymers, polyvinyl alcohols, acrylic resins, polystyrene, styrenecopolymers, polyisobutylene, hydrocarbon resins, polypropylene,polyamide resins, and polyester resins; bonding materials, for example,thermosetting resins such as urea resins, phenol resins, epoxy resins,and polyisocyanate resins, composite polymer-type bonding agents such aspolyvinyl acetal/phenol resin, rubber/phenol resin, and epoxyresin/nylon resin, rubber-based bonding materials, for example, rubberlatex-type bonding agents, and hydrophilic natural polymer bondingagents such as starch, glue and casein; and pressure-sensitiveadhesives, for example, solvent type pressure-sensitive adhesives,emulsion type pressure-sensitive adhesives, hot melt-typepressure-sensitive adhesives and delayed type pressure-sensitiveadhesives.

[0131] The shaping base is formed from a member selected from polymerfilms, for example, regenerated cellulose, polyethylene, polypropylene,soft polyvinyl chloride resin, hard polyvinyl chloride resin, andpolyester films; surface-smoothed paper sheets, for example,glassine-paper sheets, coated paper sheets, for example,polyethylene-laminated paper sheets, resin-impregnated paper sheets andmetallized paper sheets; metal foils, for example, aluminum foil, andsynthetic paper sheets; and plates of inorganic glasses, metals andplastics, which have a high smooth surface. Especially, polymer films,for example, polyethylene, polypropylene and polyester films,polyethylene-laminated paper sheets, glassine paper sheets and inorganicglass plates and metal plates are advantageously used for the shapingbase, because they can be easily coated with a coating liquid for theink-receiving layer and allow the resultant laminate to be easilyseparated from the shaping base.

[0132] To obtain a high gloss ink-receiving layer, the shaping base hasa shaping surface with a high smoothness. The shaping surface preferablyhas a surface roughness Ra of 0.5 μm or less, more preferably, 0.05 μmor less, determined in accordance with Japanese Industrial Standard(JIS) B 0601.

[0133] The shaping base surface can be used without applying any surfacetreatment thereto. To enhance the release property of the resultantink-receiving layer from the shaping base, the shaping surface ispreferably coated with a releasing agent, for example, a silicone resinor fluorine-containing resin. Also, to enhance the affinity of theshaping base surface to the coating liquid for the ink-receiving layer,the shaping base surface may be hydrophillized by applying acorona-discharge treatment or a plasma treatment thereto.

[0134] Where an additional ink-absorbent layer is contained in the inkjet recording material, firstly the shaping base surface is coated withthe ink-receiving layer and then with the additional ink-absorbentlayer. Then the substrate is bonded to the additional ink absorbentlayer formed on the ink-receiving layer, through an intermediate layeror without using the intermediate layer. In this case, at least the inkreceiving layer, contains fine pigment particles having an averageparticle size of 50 nm or less, preferably pigment secondary particleshaving an average secondary particle size of 10 to 300 nm, still morepreferably the above-mentioned silica or aluminosilicate secondaryparticles.

[0135] In an embodiment of the process of the present invention forproducing the ink jet recording material, the ink-receiving layer formedon the shaping base is directly bonded to the substrate which may becoated with an additional ink-absorbent layer, without using theintermediate layer.

[0136] Generally, it has been realized that the dry ink-receiving layercannot be directly bonded to the substrate when no adhesive intermediatelayer is used. The inventors of the present invention attempted tofirmly bond the dry ink-receiving layer to the substrate without using abonding material and found that the dry ink-receiving layer formed onthe shaping base surface can be firmly bonded to the substrate with abonding strength (mainly derived from Van Der Waals attractiontherebetween) higher than the adhesive strength between the dryink-receiving layer and the shaping base surface, by controlling thebonding temperature and the bonding pressure between the dryink-receiving layer and the substrate superposed on the ink-receivinglayer. In this case, the resultant laminate can be separated from theshaping base surface without separation between them, and the resultantink jet recording material has high smoothness and high gloss and canrecord thereon ink images with a high color density and clarity.

[0137] The same firm bonding as mentioned above can be attained evenwhen the substrate is bonded to an additional ink-absorbent layer formedon the shaping base. Similarly, the additional ink-absorbent layerbonded to the substrate can be firmly bonded to the ink-receiving layerformed on the shaping base. Also, two or more additional ink-absorbentlayers successively formed on the shaping base can be successivelybonded on the substrate in the above-mentioned way and finally, firmlybonded to the ink-receiving layer formed on the shaping base. In thiscase, each additional ink-receiving layer separated from the shapingbase has a smooth surface and thus can be firmly bonded to an adjacentadditional ink-absorbent layer or to the ink-receiving layer by thepress-bonding procedure without using the bonding material, andresultant composite coating layer consisting of the additionalink-absorbent layer(s) and the ink-receiving layer exhibits an enhancedresistance to cracking.

[0138] In the process of the present invention for producing the ink jetrecording material, the press bonding of the ink-receiving layer to thesubstrate or the additional ink-absorbent layer bonded to the substrateis preferably carried out after wetting at least one of theink-receiving layer and the substrate or the additional ink-absorbentlayer on the substrate with a small amount of water or water vapor. Thewater or water vapor is contributory to enhancing the bonding strengthand/or the bonding rate of the ink-receiving layer to the substrate orthe additional ink-absorbent layer on the substrate.

[0139] In the process of the present invention for producing the ink jetrecording material, the content of water or solvent in the ink-receivinglayer or the additional ink-absorbent layer formed on the shaping baseis preferably controlled to a level of 50% by weight or less, morepreferably 20% by weight or less, still more preferably 10% by weight orless, based on the total dry weight of the layer. Compared with thisprocess, if a conventional wet laminating method is applied, thesubstrate paper sheet may have a wavy or corrugated surface. Also, inthe conventional wet laminating method, a wet resin layer laminated onthe substrate must be dried, and thus the substrate must have a porousstructure which will allow a vapor of water or solvent to permeatetherethrough. The above-mentioned process of the present invention issubstantially free from the above-mentioned disadvantageous of the wetlamination method.

[0140] In the process of the present invention for producing the ink jetrecording material, the ink-receiving layer formed on the shaping baseis directly press-bonded to the substrate or to the additionalink-absorbent layer. There is no specific limitation to the bondingpressure. Usually, the press-bonding is carried out preferably under alinear pressure of 1 to 250 kg/cm, more preferably 3 to 120 kg/cm. Ifthe bonding pressure is too low, the resultant bonding strength betweenthe ink-receiving layer and the substrate or the additionalink-absorbent layer may be unsatisfactory. Also, if the bonding pressureis too high, the ink-receiving layer and/or the substrate or thelaminate of the additional ink-absorbent layer and the substrate may becrushed and the ink-absorption capacity of the ink receiving layerand/or the additional ink-absorbent layer may be significantlydecreased.

[0141] The press-bonding apparatus is not limited to a specificapparatus. Usually, a super calendar is preferably utilized for thepress-bonding. Also, the super calendar preferably has a pair of metalrollers which have a high resistance to damage, deformation, and wearand a high durability in practical use.

[0142] In the press-bonding procedure, the bonding temperature is notlimited to a specific temperature. Usually, the press-bonding is carriedout preferably at a temperature of 35 to 150° C., more preferably 50 to100° C. The bonding heat is supplied from, for example, bonding rolls,to the objects to be bonded. If the bonding temperature is too low, theresultant bonding strength between the ink-receiving layer and thesubstrate or the additional ink-absorbent layer may be unsatisfactory.Also, if the bonding temperature is too high, the ink-receiving layer,the substrate and/or the additional ink-absorbent layer may be crushedor deformed. Practically, the press-bonding procedure is carried outunder the above-mentioned pressure while heating.

[0143] When water or water vapor is supplied to the ink-receiving layer,the substrate or the additional ink-absorbent layer to be subjected tothe press-bonding procedure, the amount of water to be contained in theabove-mentioned layer or substrate is not limited to a specific amount.Usually, the amount of water is controlled preferably to 0.1 to 10 g/m²,more preferably 2 to 8 g/m². If the water amount is too small, thebonding effect may not be satisfactorily promoted. If the water amountis too much, the bonding effect may be saturated.

[0144] When water or water vapor is absorbed by at least one of theabove-mentioned layers and substrate, the close contact between thelayers or substrate is promoted and thus the bonding strength isenhanced and the transfer of the ink-receiving layer from the shapingbase to the substrate side can be easily effected. By applying water orwater vapor, the necessary bonding temperature and/or pressure can bereduced. For applying water, a conventional coating device, for example,blade coater, air knife coater, roll coater, bar coater, gravuor coater,rod blade coater, lip coater or curtain coater can be utilized.

[0145] When water vapor is used, the ink-receiving layer and theadditional ink-absorbent layer which have a plurality of pores forabsorbing the ink, and a porous substrate, for example, paper sheet, canrapidly absorb the water vapor in the pores and wetted with water. Thewater vapor method can accurately and uniformly control the amount ofwater absorbed by the above-mentioned layers or substrate, so as toprevent the uneven shrinkage or elongation of the layers or substrate.

[0146] When water vapor is used, the amount of water absorbed by theink-receiving layer, the substrate or the additional ink-absorbent layeris preferably controlled to 5 to 300%, more preferably 10 to 150%, stillmore preferably 20 to 100%, based on the absolute dry weight of theabove-mentioned ink-receiving layer, substrate or additionalink-absorbent layer. If the water vapor is absorbed in too small anamount, the bonding-promotion effect of water vapor may be insufficient,and the ink-receiving layer may not be smoothly transferred. Also, ifthe absorbed amount of water vapor is too large, the ink-receiving layeror the additional ink-absorbent layer may be deformed (shrunk orelongated) during the press-bonding procedure, and the deformation maycauses the resultant ink jet recording material to be curled afterdrying.

[0147] The water vapor can be supplied by utilizing a watervapor-spouting device (which is attached to a coating apparatus and usedfor controlling curling of the resultant ink jet recording material), anultrasonic water vapor-generating device or other water vapor-generatingdevice.

[0148] The ink applicable for the ink jet recording material of thepresent invention can be selected from conventional inks for the ink jetrecording system.

[0149] The ink comprises, as indispensable components, a coloringmaterial for forming visual images and a liquid medium for dissolving ordispersing the coloring material therein and, as optional components, adispersing agent, surfactant, viscosity-regulating agent, specificresistance regulating agent, pH-regulating agent, mildewproofing agent,and solution or dispersion-stabilizer for the coloring material.

[0150] The coloring material for the ink for the present invention isnot limited to specific materials. Usually, the coloring material isselected from direct dyes, acid dyes, basic dyes, reactive dyes,coloring matters for foods, disperse dyes, oil dyes and coloringpigments. The content of the coloring material is variable depending onthe type of the coloring material, the type of the liquid medium andproperties required to the ink. Usually, the coloring material iscontained in a concentration of 0.1 to 20% by weight in the ink usablefor the ink jet recording material of the present invention.

[0151] The liquid medium for the ink is usually selected from water andwater-soluble organic solvents, for example, alkyl alcohols having 1 to4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol,isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol; ketones andketone alcohols, for example, acetone and diacetone alcohol;polyalkylene glycols, for example, polyethylene glycol and polypropyleneglycols; alkylene glycols of which the alkylene group has 2 to 6 carbonatoms, for example, ethylene glycol, propylene glycol, butylene glycol,triethylene glycol, thiodiglycol, hexylene glycol and diethylene glycol;amide compounds, for example, dimethylformamide; ether compounds, forexample, tetrahydrofuran, and lower alkyl ethers of polyhydric alcohols,for example, ethyleneglycol methyl-ether, diethyleneglycol methyl (orethyl) ether, triethyleneglycol monomethyl ether.

EXAMPLES

[0152] The present invention will be further illustrated by thefollowing examples.

Example Group I Examples I-1 to I-13 and Comparative Examples I-1 to I-9

[0153] In Example Group I, the following pigments were used.

[0154] (1) Silica colloidal particles A-1

[0155] An aqueous colloidal solution of silica colloidal particles A-1having a concentration of 8% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 16 nm and an average secondary particle size of 9 μmand available under a trademark of Nipsil LP from Nihon Silica KogyoK.K. in water and pulverizing the particles by repeating a combinationof a sand grinder treatment and an ultrasonic homogenizer treatmentuntil the average secondary size of the pulverized silica particlesreached 50 nm.

[0156] (2) Silica colloidal particles B-1

[0157] An aqueous colloidal solution of silica colloidal particles B-1having a concentration of 12% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 21 nm and an average secondary particle size of 9 μmand available under a trademark of Nipsil NS from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 100nm.

[0158] (3) Silica colloidal particles C-1

[0159] An aqueous colloidal solution of silica colloidal particles C-1having a concentration of 15% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 11 nm and an average secondary particle size of 3 μmand available under a trademark of Nipsil HD-2 from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 200nm.

[0160] (4) Silica colloidal particles D-1

[0161] An aqueous colloidal solution of comparative silica colloidalparticles D-1 having a concentration of 15% by weight was prepared bydispersing wet method synthetic amorphous silica particles having anaverage primary particle size of 16 nm and an average secondary particlesize of 9 μm and available under a trademark of Nipsil LP from NihonSilica Kogyo K.K. in water and pulverizing by repeating a combination ofa sand grinder treatment and an ultrasonic homogenizer treatment untilthe average secondary size of the pulverized silica particles reached500 nm.

[0162] (5) Aluminosilicate particles A

[0163] Isopropyl alcohol in an amount of 100 g was charged in a glassreactor having a capacity of 2 liters and equipped with a separableflask, 3 agitating blades each having a diameter of 3 cm and athermometer and heated to a temperature of 60° C. by using an oil bathheater. Then, 5g of aluminum isopropoxide was added to isopropyl alcoholwhile agitating the resultant reaction mixture with the 3 agitatingblades at a rotation of 100 rpm. Thereafter, 1.0 g of an acid catalystconsisting of acetic acid was added to the reaction mixture and theagitation was continued, while refluxing at the above-mentionedtemperature, for 24 hours.

[0164] Separately, 100 g of ion-exchanged water was charged in the sametype of the glass reactor as mentioned above, and heated to atemperature of 60° C., 1.8 g of ethyl orthosilicate were added to thewater, 1 g of an acid catalyst consisting of nitric acid was added tothe resultant solution, and then the reactant reaction mixture wasagitated at the above-mentioned temperature for 24 hours, whilerefluxing.

[0165] The ethyl orthosilicate-nitric acid-ion-exchanged water-reactionproduct solution was mixed into the aluminum isopropoxide-aceticacid-isopropyl alcohol-reaction product solution, the resultant reactionmixture was agitated at a temperature of 60° C. for 6 hours, to producealuminosilicate fine particles. The resultant dispersion wasconcentrated at a temperature of 60° C. in an evaporator, to obtainagglomerated secondary particles of aluminosilicate. In thealuminosilicate secondary particles, the molar ratio of alumina tosilica was 3:2. The primary particles of the aluminosilicate had anaverage primary particle size of 10 nm.

[0166] The aluminosilicate secondary particles were diluted with waterand pulverized by repeating a combination of a sand grinder treatmentwith an ultrasonic homogenizer treatment until the average secondaryparticle size of the aluminosilicate particles reached 60 nm. Theresultant aqueous colloidal solution of the aluminosilicate secondaryparticles had a concentration of 8% by weight.

Example I-1

[0167] An aqueous silica colloidal coating solution having a solidcontent of 8% by solid weight was prepared from the silica colloidalsolution A-1 in an amount of 100 parts by solid weight, and 40 parts byweight of polyvinyl alcohol (available under the trademark of PVA-124,from Kuraray Co., Ltd.) having a degree of polymerization of 2400 and adegree of saponification of 98.5%.

[0168] A substrate sheet was prepared by laminating a surface of acoated paper sheet (available under the trademark of OK Coat from OJIPAPER CO. Ltd.) having a basis weight of 127.9 g/m² with a polyethyleneresin layer having a thickness of 15 pn by an extrusion-laminatingmethod. This polyethylene resin-laminated paper sheet will be referredto as a laminated paper sheet hereinafter.

[0169] The aqueous silica colloidal coating solution was coated on asurface of the laminated paper sheet by using a Mayer bar and dried toform an ink-receiving layer with a dry weight of 20 g/m².

[0170] An ink jet recording sheet was obtained.

Example I-2

[0171] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that in place of the polyvinyl alcohol (PVA-124),another polyvinyl alcohol (available under the trademark of PVA-117,from Kuraray Co., Ltd.) having a degree of polymerization of 1800 and adegree of saponification of 98.5% was used.

Example I-3

[0172] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that in place of the polyvinyl alcohol (PVA-124),another polyvinyl alcohol (available under the trademark of PVA-224,from Kuraray Co., Ltd.) having a degree of polymerization of 2400 and adegree of saponification of 88.5% was used.

Example I-4

[0173] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that in place of the polyvinyl alcohol (PVA-124),another polyvinyl alcohol (available under the trademark of PVA-135H,from Kuraray Co., Ltd.) having a degree of polymerization of 3500 and adegree of saponification of 99% or more was used.

Example I-5

[0174] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that in place of the polyvinyl alcohol (PVA-124),another polyvinyl alcohol (available under the trademark of PVA-140H,from Kuraray Co., Ltd.) having a degree of polymerization of 4000 and adegree of saponification of 99% or more was used.

Example I-6

[0175] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that an aqueous silica colloidal coating solutionhaving a solid content of 12% by weight was prepared from the silicacolloidal solution B-1 in an amount of 100 parts by solid weight and 40parts by weight of the polyvinyl alcohol (PVA-124), and coated on thelaminated paper sheet to form an ink-receiving layer in a dry amount of20 g/m².

Example I-7

[0176] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that an aqueous silica colloidal coating solutionhaving a solid content of 15% by weight was prepared from the silicacolloidal solution C-1 in an amount of 100 parts by solid weight and 40parts by weight of the polyvinyl alcohol (PVA-124), and coated on thelaminated paper sheet to form an ink-receiving layer in a dry weight of20 g/m².

Example I-8

[0177] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that the aqueous silica colloidal coating solutionwas coated on a surface of a shaping base consisting of a polyethyleneterephthalate film (available under the trademark of Lumilar T fromToray) having a thickness of 75 μm and a surface roughness Ra of 0.02μm, and dried, to form a coating layer having a dry weight of 20 g/m².

[0178] Then, an polyacrylic acid adhesive (available under the trademarkof A-02, from Nihon Carbide Kogyo K.K.) was coated on a surface of thedried colloidal silica layer and dried to form an intermediate layerhaving a dry weight of 10 g/m².

[0179] The intermediate layer on the dried colloidal silica layer wassuperposed on and press-bonded to the laminated paper sheet under alinear pressure of 50 kg/cm by using a calender. Then the resultantlaminate was separated from the shaping base film, to provide an ink jetrecording sheet.

Example I-9

[0180] An aqueous aluminosilicate colloidal solution having a solidcontent of 8% by weight was prepared from the aluminosilicate colloidalsolution A in an amount of 100 parts by solid weight and 40 parts byweight of polyvinyl alcohol (available under the trademark of PVA-135H,from Kuraray Co., Ltd.) having a degree of polymerization of 3500 and adegree of saponification of 99% or more.

[0181] The aqueous aluminosilicate colloidal coating solution was coatedon a surface of the laminated paper sheet by using a Mayer bar and driedto form an ink-receiving layer with a dry weight of 20 g/m².

[0182] An ink jet recording sheet was obtained.

Comparative Example I-1

[0183] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that an aqueous silica colloidal coating solutionhaving a solid content of 15% by weight was prepared from the silicacolloidal solution D-1 in an amount of 100 parts by solid weight and 40parts by weight of the polyvinyl alcohol (PVA-124), and coated on thelaminated paper sheet to form an ink receiving layer in a dry weight of20 g/m².

Comparative Example I-2

[0184] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that an aqueous silica dispersion having a solidcontent of 15% by weight was prepared from 100 parts by solid weight ofwet method synthetic amorphous silica particles (available under atrademark of Nipsil HD-2, from Nihon Silica Kogyo K.K.) having anaverage primary particle size of 11 nm and an average secondary particlesize of 3 μm and 40 parts by weight of polyvinyl alcohol (PVA-124), andcoated on a surface of the laminated paper sheet by using a Mayer barand dried to form an ink-receiving layer having a dry weight of 20 g/m².

Comparative Example I-3

[0185] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that an aqueous silica dispersion having a solidcontent of 15% by weight was prepared from 100 parts by solid weight ofwet method synthetic amorphous silica particles (available under atrademark of Nipsil LP, from Nihon Silica Kogyo K.K.) having an averageprimary particle size of 16 nm and an average secondary particle size of9 μm, and 40 parts by weight of polyvinyl alcohol (PVA-124), and coatedon a surface of the laminated paper sheet by using a Mayer bar and driedto form an ink-receiving layer having a dry weight of 20 g/m².

Comparative Example I-4

[0186] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that an aqueous alumina dispersion having a solidcontent of 8% by weight was prepared from 100 parts by solid weight ofprimary alumina particles (available under a trademark of Aluminasol-100, from Nissan Kagakukogyo K.K.) having average minor and majoraxes of primary particles of 10 nm and 100 nm, respectively, and 40parts by weight of polyvinyl alcohol (PVA-124), and coated on a surfaceof the laminated paper sheet by using a Mayer bar and dried to form anink-receiving layer having a dry weight of 20 g/m².

Comparative Example I-5

[0187] An ink jet recording sheet was prepared by the same procedures asin Example I-1 except that an aqueous silica dispersion having a solidcontent of 15% by weight was prepared from 100 parts by solid weight ofan anionic primary silica particle colloidal solution (available under atrademark of Snowtex YL, from Nissan Kagakukogyo K.K.) having an averageprimary particle size of 65 nm, and 10 parts by weight of polyvinylalcohol (PVA-124), and coated on a surface of the laminated paper sheetby using a Mayer bar and dried to form an ink-receiving layer having adry weight of 20 g/m².

Comparative Example I-6

[0188] An aqueous coating liquid having a solid content of 15% by weightwas prepared from 100 parts by solid weight of thesilica colloidalsolution A-1 and 100 parts by solid weight of a styrene-butadienecopolymer latex (trademark: Nipol LX 415A, made from Nihon Zeon Co.,Ltd.) having an average particle size of 110 nm and a Tg of 27° C.

[0189] The aqueous coating layer was coated on a surface of thelaminated paper sheet by using a Mayer bar and dried to form anink-receiving layer having a dry weight of 20 g/m². An ink jet recordingsheet was obtained.

Comparative Example I-7

[0190] An aqueous solution of 10% by weight of a polyvinyl alcoholhaving a degree of polymerization of 1800 and a degree of saponificationof 98.5% (available under a trademark of PVA-117, from Kuraray Co.,Ltd.) was coated on a surface of the laminated paper sheet by using aMayer bar to form an ink-receiving layer having a dry weight of 20 g/m².An ink jet recording sheet was obtained.

Comparative Example I-8

[0191] A gloss ink jet recording sheet having an ink-fixing layer and agloss layer (available under the trademark of GP-101, from Canon Corp.)was subjected to the tests explained below.

Comparative Example I-9

[0192] An ink jet recording sheet was prepared by the followingprocedures.

[0193] (1) Composition of a coating solution for forming anink-receiving layer (i) Dry method silica fine 10 parts by weightparticles (average primary particle size: 7 nm, refractive index: 1.45,number of silanol groups on surface: 2-3/nm², trademark: Aerosil A300(available from Nippon Aerosil Co., Ltd.)) (ii) Polyvinyl alcohol 3.3parts by weight (saponification degree: 88%, polymerization degree:3,500, trademark: PVA23 (available from Kuraray Co., Ltd.)) (iii) Ionexchanged water 136.0 parts by weight

[0194] The dry method silica fine particles (i) are introduced into apart of the ion exchanged water (iii) (73.3 parts by weight) anddispersed therein at 10,000 rpm for 20 minutes using a high-speed rotarywet colloid mill (Creamix, produced by M Technique Co. Ltd.). To theresulting dispersion was added an aqueous polyvinyl alcohol solution(solution obtained by dissolving polyvinyl alcohol in the remainder(62.7 parts by weight) of the ion exchanged water (iii)), and dispersingwas carried out. Then, pH was adjusted to 4 to 5, to obtain a coatingsolution for forming an ink-receiving layer.

[0195] (2) Coating and drying

[0196] The coating solution was coated on a surface of the samelaminated paper sheet as in Example I-1 by using a Mayer bar and driedto form an ink-receiving layer having a dry weight of 20 g/m². An inkjet recording sheet was obtained.

[0197] The ink jet recording sheets of Examples I-1 to I-9 andComparative Examples I-1 to I-9 were subjected to the followingwater-resistance, ink-absorption and ink absorption capacity tests.

[0198] The specimens of the ink recording sheets of Examples I-1 to I-9and Comparative Examples I-1 to I-7 were calender-treated under a linearpressure of 20 kg/cm before the tests.

[0199] The gloss and ink-absorbing properties were represented by agloss, an ink-absorption and color density of ink images of a solidprinted portion of the specimen printed by a practical ink jet printer(trademark: BJC-600J, made by Canon Inc.).

[0200] [Water Resistance]

[0201] A water drop was placed on the ink-receiving layer surface of thespecimen, 30 minutes after the water drop-placing, the water drop waswiped out, the water drop-placed portion of the specimen was rubbed witha finger, and the rubbing result was evaluated in the following fourclasses.

[0202] 4 . . . No change appears in the ink-receiving layer portion.

[0203] 3 . . . The ink-receiving layer portion was slightly removed.

[0204] 2 . . . The ink-receiving layer portion was certainly removed.

[0205] 1 . . . The ink-receiving layer portion was completely removed.

[0206] [Ink Absorption]

[0207] (a) Ink absorbing rate

[0208] Each of yellow, magenta and cyan-colored inks was printed on thespecimen, every 5 seconds after the printing, a woodfree paper sheet wasput on the ink-printed portion of the specimen, and it was observedwhether or not the ink was transferred to the paper sheet. The timenecessary to completely fix the ink in the ink receiving layer so thatno ink transfer occurred on the specimen was determined. The inkabsorption rate was evaluated in four classes as follows.

[0209] 4 . . . Less than 5 seconds

[0210] 3 . . . 5 seconds or more but less than 10 seconds

[0211] 2 . . . 10 seconds or more but less than 30 seconds

[0212] 1 . . . 30 seconds or more

[0213] The specimen having an ink-fixing time of less than 10 seconds isevaluated as to be excellent in ink-absorbing rate.

[0214] (b) Ink absorption capacity

[0215] On a portion having an area of 10 cm×10 cm of a A4 size specimen,yellow, magenta and cyan-colored inks were successively solid-printed.To observe whether or not the inks flowed out from the solid printedportion of the specimen, a woodfree paper sheet was put on the solidprinted portion of the specimen at each stage of immediately one minute,2 minutes and 5 minutes after the printing, and it was observed whetheror not the inks were transferred to the paper sheet, to determine thetime necessary to completely fix the inks in the ink-receiving layer sothat no ink transfer occurred to the paper sheet. The results wereevaluated in the following four classes.

[0216] 4 . . . Less than one minute

[0217] 3 . . . One minute or more but less than 2 minutes

[0218] 2 . . . 2 minutes or more but less than 5 minutes

[0219] 1 . . . 5 minutes or more

[0220] [Color Density of Ink Images]

[0221] A solid printing was applied with a black colored ink on thespecimen.

[0222] The color density of the black colored ink images was measured byusing a Macbeth reflection color density tester (Model RD-920). Themeasurement was repeated 5 times and the color density was representedby an average value of the measured values.

[0223] [Gloss of Printed Portion]

[0224] The gloss of ink-printed portion of the specimen was determinedby observing the ink-printed portion at an angle of 20 degrees from thesurface of the specimen by the-naked eye and evaluated in the followingfour classes.

[0225] 4 . . . Very high gloss substantially equal to the gloss ofconventional full color-printed silver salt type photographic printingsheets

[0226] 3 . . . High gloss but slightly lower than the gloss of the fullcolor printed photographic printing sheets

[0227] 2 . . . Similar to the gloss of printed coated paper sheets

[0228] 1 . . . Similar to the gloss of printed PPC sheets

[0229] [Form of Ink Dots]

[0230] The form of the printed ink dots was observed by a microscope ata magnification of 100 to 200.

[0231] The test results are shown in Table 1. TABLE 1 Ink absorption Inkabsorption Ink absorption Water Color density Gloss of Form of inkExample No. rate capacity resistance of ink images printed portion dotsExample I-1 4 4 4 2.20 3 True circle I-2 3 3 4 2.19 3 ″ I-3 4 4 3 2.19 3″ I-4 4 4 4 2.23 3 ″ I-5 4 4 4 2.23 3 ″ I-6 4 4 4 1.91 3 ″ I-7 4 4 41.70 3 ″ I-8 4 4 4 2.27 3 ″ I-9 4 4 4 2.12 3 ″ Comparative I-1 4 4 41.15 3 True circle Example I-2 4 4 2 1.30 1 Irregular (cloud-like) I-3 44 2 1.21 1 Irregular (cloud-like) I-4 1 1 4 2.25 3 True cirle I-5 4 1 41.87 3 ″ I-6 1 2 4 2.06 3 ″ I-7 1 1 1 2.40 2 circle I-8 4 4 4 1.41 2Irregular (cloud-like) I-9 2 4 2 2.10 2 Irregular (cloud-like)

[0232] Table 1 clearly shows that in the ink jet recording sheets ofExamples I-1 to I-9 in accordance with the present invention, theink-receiving layers had satisfactory ink-absorbing properties and waterresistance, the ink dots had a true circle form and the printed inkimages had a high gloss, a high color density, and satisfactory clarityand sharpness. However, the ink jet recording sheets of Comparativeexamples were unsatisfactory in one or more of the above-testedperformances.

[0233] The above-mentioned excellent properties of the ink jet recordingmaterial of the present invention are derived from the specific silicaor aluminosilicate colloidal particles contained in the ink-receivinglayer. The secondary particles of silica or aluminosilicate usable forthe present invention each comprising a plurality of primary particleswhich have a sphere form, exhibit an enhanced film-forming property andink-absorbing property and thus the resultant ink-receiving layerexhibits a high resistance to cracking and excellent ink-absorbingproperty and the ink images recorded in the ink-receiving layer havehigh color density and clarity.

Example Group II Examples II-1 to II-8 and Comparative Examples II-1 toII-4

[0234] In Example Group II, the following pigments were used.

[0235] (1) Silica colloidal particles A-2

[0236] An aqueous colloidal dispersion of silica colloidal particles A-2having a concentration of 8% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 13 nm and an average secondary particle size of 2 μmand available under a trademark of Nipsil HD from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 40 nm.

[0237] (2) Silica colloidal particles B-2

[0238] An aqueous colloidal dispersion of silica colloidal particles B-2having a concentration of 12% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 15 nm and an average secondary particle size of 2.2 μmand available under a trademark of Nipsil K-300 from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 90 nm.

[0239] (3) Silica colloidal particles C-2

[0240] An aqueous colloidal dispersion of silica colloidal particles C-2having a concentration of 12% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 24 nm and an average secondary particle size of 1.5 μmand available under a trademark of Nipsil E-1011 from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 120nm.

[0241] (4) Silica colloidal particles D-2

[0242] An aqueous colloidal dispersion of silica colloidal particles D-2having a concentration of 15% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 13 nm and an average secondary particle size of 2 μmand available under a trademark of Nipsil HD from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 240nm.

[0243] (5) Aluminosilicate colloidal particles A

[0244] They are as mentioned above.

Example II-1

[0245] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was prepared from the silica colloidaldispersion A-2 in an amount of 100 parts by solid weight and 40 parts byweight of polyvinyl alcohol (available under the trademark of PVA-135H,from Kuraray Co., Ltd.) having a degree of polymerization of 3500 and adegree of saponification of 99% or more.

[0246] A substrate sheet was prepared by laminating a surface of acoated paper sheet (available under the trademark of OK Coat from OJIPAPER CO., Ltd.) having a basis weight of 127.9 g/m² with a polyethyleneresin layer having a thickness of 15 μm by an extrusion-laminatingmethod. This polyethylene resin-laminated paper sheet will be referredto as a laminated paper sheet hereinafter.

[0247] The aqueous silica colloidal coating solution was coated on asurface of the laminated paper sheet by using a Mayer bar and dried toform an ink-receiving layer with a dry weight of 20 g/m².

[0248] An ink jet recording sheet was obtained.

[0249] A pore radius distribution curve was prepared for the resultantink-receiving layer. In this curve, a peak corresponding to a poreradius of 8 nm was found as shown in FIG. 1. The measurement of the poreradius was carried out for the pore radius of from 3 nm to 100 μm. Inthis measurement, only one peak was found at the pore radius of 8 nm.

[0250] In the ink-receiving layer, the integrated pore volume of all thepores was about 0.86 ml/g and the total volume of the pores having apore radius of from 3 to 20 nm was 0.6 ml/g.

Example II-2

[0251] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous silica colloidal coatingsolution having a solid content of 12% by weight was prepared from thesilica colloidal dispersion B-2 in an amount of 100 parts by solidweight and 40 parts by weight of the polyvinyl alcohol (PVA-135H), andcoated on the laminated paper sheet by a Mayer bar and dried, to form anink-receiving layer having a dry weight of 20 g/m². The pore radiusdistribution curve of the ink-receiving layer had a peak correspondingto a pore radius of 18 nm.

Example II-3

[0252] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous silica colloidal coatingsolution having a solid content of 12% by weight was prepared from thesilica colloidal dispersion C-2 in an amount of 100 parts by solidweight and 40 parts by weight of the polyvinyl alcohol (PVA-135H), andcoated on the laminated paper sheet by a Mayer bar and dried, to form anink-receiving layer having a dry weight of 20 g/m². The pore radiusdistribution curve of the resultant ink-receiving layer had two peakscorresponding to pore radiuses of 4 nm and 35 nm. The ink-receivinglayer had an integrated pore volume of 1.1 ml/g and a total volume ofthe pores having a pore radius of 3 to 20 nm of 0.6 ml/g.

Example II-4

[0253] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous aluminosilicate colloidalcoating solution having a solid content of 8% by weight was preparedfrom the aluminosilicate colloidal dispersion A in an amount of 100parts by solid weight and 40 parts by weight of the polyvinyl alcohol(PVA-135H), and coated on the laminated paper sheet by a Mayer bar anddried, to form an ink-receiving layer having a dry weight of 20 g/m².The pore radius distribution curve of the resultant ink-receiving layerhad a peak corresponding to a pore radius of 10 nm.

Example II-5

[0254] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous silica colloidal coatingsolution having a solid content of 8% by weight was prepared from thesilica colloidal dispersion A-2 in an amount of 100 parts by solidweight and 40 parts by weight of the polyvinyl alcohol (PVA-135H), andcoated on a surface of a shaping base consisting of a polyethyleneterephthalate (PET) film having a thickness of 75 μm and a surfaceroughness of 0.02 μm (trademark: Lumilar T, made by Toray Industries,Inc.) by a Mayer bar and dried, to form a coating layer corresponding toan ink-receiving layer and having a dry weight of 20 g/m².

[0255] Separately, a surface of the laminated paper sheet was coatedwith an acrylic ester adhesive (trademark: A-02, made by Nippon CarbideIndustries Co., Inc.) and dried to form an intermediate layer in a dryamount of 10 g/m².

[0256] Then, the intermediate layer of the laminated paper sheet wassuperposed on and press-bonded to the coating layer on the shaping baseunder a linear pressure of 20 kg/cm by using a calender. The resultantlaminate was separated from the shaping base, to provide an ink jetrecording sheet. The pore radius distribution curve of the ink-receivinglayer had a peak corresponding to a pore radius of 8 nm.

Example II-6

[0257] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous silica colloidal coatingsolution having a solid content of 8% by weight was prepared from thesilica colloidal dispersion A-2 in an amount of 100 parts by solidweight and 40 parts by weight of the polyvinyl alcohol (PVA-135H), andcoated on a surface of the same shaping base as in Example II-5 by aMayer bar and dried, to form a coating layer corresponding to anink-receiving layer having a dry weight of 10 g/m².

[0258] On the coating layer on the shaping base, an aqueous silicacolloidal coating solution prepared from the silica colloidal dispersionB-2 in an amount of 100 parts by solid weight and the polyvinyl alcohol(PVA-135H) in an amount of 40 parts by solid weight and having a solidcontent of 12% by solid weight was coated by using a Mayer bar anddried, to form an additional coating layer corresponding to anadditional ink-absorbent layer and having a dry weight of 20 g/m².

[0259] Separately, a surface of the laminated paper sheet was coatedwith an acrylic ester adhesive (trademark: A-02, made by Nihon CarbideKogyo K.K.) and dried to form an intermediate layer in a dry amount of10 g/m².

[0260] Then, the intermediate layer of the laminated paper sheet wassuperposed on and press-bonded to the additional coating layer of theshaping base under a linear pressure of 20 kg/cm by using a calender.The resultant laminate was separated from the shaping base, to providean ink jet recording sheet. The pore radius distribution curve of theink-receiving layer had a peak corresponding to a pore radius of 8 nm.

Example II-7

[0261] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous silica colloidal coatingsolution having a solid content of 8% by weight was prepared from thesilica colloidal dispersion A-2 in an amount of 100 parts by solidweight and 40 parts by weight of the polyvinyl alcohol (PVA-135H), andcoated on the surface of the same shaping base as in Example II-5 by aMayer bar and dried, to form a coating layer corresponding to anink-receiving layer having a dry weight of 20 g/m² On the surface of thecoating layer formed on the shaping base, an aqueous silica dispersionprepared from 100 parts by solid weight of wet method syntheticamorphous silica particles having an average primary particle size ofabout 15 nm and an average secondary particle size of 4.5 μm (availableunder a trademark of Finesil X-45, from Tokuyama Corp.) and 40 parts bysolid weight of a polyvinyl alcohol having a degree of polymerization of1800 and a degree of saponification of 98.5% (available under atrademark of PVA-117, from Kuraray Co., Ltd.), and having a solidcontent of 15% by weight, was coated by using a Mayer bar and dried, toform an additional coating layer corresponding an additionalink-absorbent layer, having a dry weight of 10 g/m².

[0262] Separately, a surface of the laminated paper sheet was coatedwith an acrylic ester adhesive (trademark: A-02, made by Nihon CarbideKogyo K.K.) and dried to form an intermediate layer in a dry amount of10 g/m².

[0263] Then, the intermediate layer of the laminated paper sheet wassuperposed on and press-bonded to the additional coating layer of theshaping base under a linear pressure of 20 kg/cm by using a calender.The resultant laminate was separated from the shaping base, to providean ink jet recording sheet. The pore radius distribution curve of theink-receiving layer had a peak corresponding to a pore radius of 8 nm.

Example II-8

[0264] An ink jet recording sheet was produced by the followingprocedures. An aqueous silica colloidal coating solution having a solidcontent of 12% by weight was prepared from the silica colloidaldispersion D-2 in an amount of 100 parts by solid weight and 40 parts byweight of the polyvinyl alcohol (PVA-135H), and coated on the laminatedpaper sheet by a Mayer bar and dried, to form an ink-receiving layerhaving a dry weight of 20 g/m². The pore radius distribution curve ofthe ink-receiving layer had a peak corresponding to a pore radius of 45nm.

Comparative Example II-1

[0265] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous silica coating solution having asolid content of 15% by weight was prepared from wet method syntheticamorphous silica particles having an average primary particle size ofabout 15 nm and an average secondary particle size of 4.5 μm (trademark:Finesil X-45, Tokuyama Corp.) in an amount of 100 parts by solid weightand 40 parts by weight of a polyvinyl alcohol having a degree ofpolymerization of 1800 and a degree of saponification of 98.5%(trademark: PVA-117, made by Kuraray Co., Ltd.), and coated on thelaminated paper sheet by a Mayer bar and dried, to form an ink-receivinglayer having a dry weight of 20 g/m². The pore radius distribution curveof the ink-receiving layer had three peaks corresponding to poreradiuses of 5 nm, 0.32 μm and 1.4 μm. In the ink-receiving layer, theintegrated pore volume of all the pore was 0.75 ml/g and the totalvolume of pores having a pore radius of 4 to 20 nm was 0.09 ml/g.

Comparative Example II-2

[0266] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous pseudoboehmite dispersion havinga solid content of 5% by weight was prepared from a pseudoboehmite solhaving an average primary particle size of 10 nm×100 nm (trademark:AS-520, made by Nissan Kagakukogyo K.K.) in an amount of 100 parts bysolid weight and 10 parts by weight of the polyvinyl alcohol (PVA-135H),and coated on the laminated paper sheet by a Mayer bar and dried, toform an ink-receiving layer having a dry weight of 20 g/m². The poreradius distribution curve of the resultant ink-receiving layer had apeak corresponding to a pore radius of 7 nm.

Comparative Example II-3

[0267] An ink jet recording sheet was produced by the same procedures asin Example II-1, except that an aqueous silica colloidal coatingsolution having a solid content of 15% by weight was prepared from ananionic primary colloidal silica particles having an average primaryparticle size of 80 nm (trademark: Snowtex ZL, made by NissanKagakukogyo K.K.) in an amount of 100 parts by solid weight and 10 partsby weight of the polyvinyl alcohol (PVA-135H), and coated on thelaminated paper sheet by a Mayer bar and dried, to form an ink-receivinglayer having a dry weight of 20 g/m². The pore radius distribution curveof the ink-receiving layer had a peak corresponding to a pore radius of13 nm.

Comparative Example II-4

[0268] A gloss ink jet recording sheet having an ink-fixing layer and agloss layer (available under the trademark of GP-101 from Canon Corp.)was subjected to the following tests. The ink-fixing layer exhibited apore radius distribution curve having a peak corresponding to a poreradius of 5 μm.

[0269] Tests

[0270] Specimens of the ink jet recording sheets of Examples II-1 toII-8 and Comparative Examples II-1 to II-4 were subjected to thefollowing tests for water resistance, the gloss, the ink-absorbing rateand ink-absorption capacity of the ink-receiving layer.

[0271] These specimens except for the specimen of Comparative ExamplesII-4 were surface-smoothed by using a super calender under a linearpressure of 70 kg/cm, before the tests.

[0272] The gloss and ink-absorption properties were tested by solidprinting the specimens of the ink jet recording sheets by a practicalink jet printer (trademark: BJC-610J, made by Canon Corp., 720 dpi×729dpi) and the gloss, the ink-absorption properties and color density ofthe solid printed ink images were measured.

[0273] [Water Resistance]

[0274] The test for water resistance was the same as in Example Group I.

[0275] [Ink Absorption]

[0276] The test for ink-absorbing rate was the same as in Example GroupI.

[0277] In the test for the ink absorption capacity, the surfaces of thespecimens were solid printed with a black-colored ink in an ink-jettingamount of 30 g/m².

[0278] [Color density]

[0279] The test for color density of the printed ink images was the sameas in Example Group I.

[0280] [Gloss]

[0281] The test for gloss of the ink-printed portion of the ink jetrecording sheet was the same as in Example Group I.

[0282] The test results are shown in Table 2. TABLE 2 Pore radiusInk-absorption corresponding to Ink-absorbing Ink-absorption Water Glossof peak in pore radius Example No. rate capacity resistance Colordensity printed portion distribution curve Example II-1 4 3 4 2.20 3 8nm II-2 4 3 4 1.99 3 18 nm II-3 4 3 4 1.85 3 4, 35 nm II-4 4 3 4 2.12 310 nm II-5 4 3 4 2.25 4 8 nm II-6 4 4 4 2.22 4 8 nm II-7 4 4 4 2.19 3 8nm II-7 4 3 4 1.70 3 45 nm Comparative II-1 4 3 2 1.27 1 5 nm Example0.32 μm 1.40 μm II-2 2 1 4 2.21 3 7 nm II-3 4 1 4 1.85 3 13 nm II-4 4 34 1.41 2 5 μm

[0283] Table 2 clearly shows that in Examples II-1 to II-8 in accordancewith the present invention, the resultant ink jet recording materialshad a high ink-absorbing rate and a high ink-absorption capacity andcould receive thereon ink images having a high gloss, color density,clarity and sharpness.

Example Group III Examples III-1 to III-9 and Comparative Examples III-1to III-3

[0284] In Example Group III, the following pigments were employed.

[0285] (1) Silica colloidal particles A-3

[0286] An aqueous colloidal dispersion of silica colloidal particles A-3having a concentration of 8% by solid weight was prepared by dispersingwet method synthetic amorphous silica particles having an averageprimary particle size of 15 nm and an average secondary particle size of2.2 μm and available under a trademark of Nipsil K-300 from Nihon SilicaKogyo K.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 40 nm.

[0287] (2) Silica colloidal particles B-3

[0288] An aqueous colloidal solution of silica colloidal particles B-3having a concentration of 12% by solid weight was prepared by dispersingwet method synthetic amorphous silica particles having an averageprimary particle size of 24 nm and an average secondary particle size of2.5 μm and available under a trademark of Nipsil E-220A from NihonSilica Kogyo K.K. in water and pulverizing by repeating a combination ofa sand grinder treatment and an ultrasonic homogenizer treatment untilthe average secondary size of the pulverized silica particles reached 80nm.

[0289] (3) Silica colloidal particles C-3

[0290] An aqueous colloidal solution of silica colloidal particles C-3having a concentration of 12% by solid weight was prepared by dispersingthe same synthetic amorphous silica particles as for the silicacolloidal particles B-3 in water and pulverizing by repeating acombination of a sand grinder treatment and an ultrasonic homogenizertreatment until the average secondary size of the pulverized silicaparticles reached 150 nm.

[0291] (4) Silica colloidal particles D-3

[0292] An aqueous colloidal dispersion of silica colloidal particles D-3having a concentration of 12% by weight was prepared by dispersing thesame synthetic amorphous silica particles as for the silica colloidalparticles A-3 in water and pulverizing by repeating a combination of asand grinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 190nm.

[0293] (5) Silica colloidal particles E-3

[0294] An aqueous colloidal solution of silica colloidal particles E-3having a concentration of 15% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 30 nm and an average secondary particle size of 3 μmand available under a trademark of Nipsil E-170 from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary size of the pulverized silica particles reached 240nm.

[0295] (6) Aluminosilicate particle A

[0296] This is the same as in Example Group I.

Example III-1

[0297] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was prepared from the silica colloidaldispersion A-3 in an amount of 100 parts by solid weight and a polyvinylalcohol having a degree of polymerization of 2400 and a degree ofsaponification of 98.5% or more (trademark: PVA-124, made by KurarayCo., Ltd.).

[0298] A substrate sheet was prepared by laminating a surface of acoated paper sheet (trademark: OK Coat, made by OJI PAPER CO. Ltd.)having a basis weight of 127.9 g/m², with a polyethylene resin layerhaving a thickness of 15 μm by an extrusion-laminating method. Thispolyethylene resin-laminated paper sheet will be referred to as alaminated paper sheet hereinafter.

[0299] The aqueous coating solution was coated on a surface of thelaminated paper sheet by using a Mayer bar and dried to form anink-receiving layer with a dry weight of 15 g/m².

[0300] An ink jet recording sheet was obtained.

Example III-2

[0301] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous silica colloidal coatingsolution having a solid content of 12% by weight was prepared from thesilica colloidal dispersion B-3 in an amount of 100 parts by solidweight and a polyvinyl alcohol having a degree of polymerization of 3500and a degree of saponification of 99% or more (trademark: PVA-135, madeby Kuraray Co., Ltd.) in an amount of 25 parts by solid weight, andcoated on the laminated paper sheet by using a Mayer bar and dried toform an ink-receiving layer having a dry weight of 15 g/m².

Example III-3

[0302] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous silica colloidal coatingsolution having a solid content of 12% by weight was prepared from thesilica colloidal dispersion C-3 in an amount of 100 parts by solidweight and the polyvinyl alcohol (PVA-124) in an amount of 50 parts bysolid weight, and coated on the laminated paper sheet by using a Mayerbar and dried to form an ink-receiving layer having a dry weight of 15g/m².

Example III-4

[0303] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that in the preparation of the an aqueoussilica colloidal coating solution having a solid content of 12% byweight, the silica colloidal dispersion A-3 was replaced by the silicacolloidal dispersion D-3.

Example III-5

[0304] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous aluminosilicate colloidalcoating solution having a solid content of 8% by weight was preparedfrom the aluminosilicate colloidal dispersion A in an amount of 100parts by solid weight and the polyvinyl alcohol (PVA-124) in an amountof 40 parts by solid weight, and coated on the laminated paper sheet byusing a Mayer bar and dried to form an ink-receiving layer having a dryweight of 15 g/m².

Example III-6

[0305] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous silica colloidal coatingsolution having a solid content of 8% by weight was prepared from thesilica colloidal dispersion A-3 in an amount of 100 parts by solidweight and the polyvinyl alcohol (PVA-124) in an amount of 40 parts bysolid weight, and coated on a surface of a shaping base consisting of apolyethylene terephthalate film (trademark: Lumilar T, made by Toray)having a thickness of 75 μm and a surface roughness Ra of 0.02 μm byusing a Mayer bar, and dried to form a coating layer corresponding to anink-receiving layer, having a dry weight of 15 g/m².

[0306] Separately, a surface of the laminated paper sheet was coatedwith an acrylic acid adhesive (trademark: A-02, made by Nihon CarbideKogyo K.K.) and dried, to form an intermediate layer having a dry weightof 10 g/m².

[0307] The intermediate layer on the laminated paper sheet wassuperposed on and press-bonded to the coating layer formed on theshaping base under a linear pressure of 20 kg/cm by using a calender.Then the shaping base film was removing from the resultant laminate toleave an ink jet recording sheet.

Example III-7

[0308] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous silica colloidal coatingsolution having a solid content of 8% by weight was prepared from thesilica colloidal dispersion A-3 in an amount of 100 parts by solidweight and the polyvinyl alcohol (PVA-124) in an amount of 70 parts bysolid weight, and coated on the laminated paper sheet by using a Mayerbar and dried to form an ink-receiving layer having a dry weight of 15g/cm².

Example III-8

[0309] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous silica colloidal coatingsolution having a solid content of 15% by weight was prepared from thesilica colloidal dispersion E-3 in an amount of 100 parts by solidweight and the polyvinyl alcohol (PVA-124) in an amount of 40 parts bysolid weight, and coated on the laminated paper sheet by using a Mayerbar and dried to form an ink-receiving layer having a dry weight of 15g/m².

Example III-9

[0310] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that the same aqueous silica colloidal coatingsolution as in Example III-2 was coated on the laminated paper sheet byusing a Mayer bar and dried to form an additional ink-absorbent layerhaving a dry weight of 10 g/m². Then, the same aqueous silica colloidalsolution as in Example III-1 was coated on the additional ink-absorbentlayer to form an ink-receiving layer having a dry weight of 10 g/m².

Comparative Example III-1

[0311] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous silica coating solution havinga solid content of 15% by weight was prepared from a wet methodsynthetic amorphous, silica particles (trademark: Finesil x-45, made byTokuyama K.K.) having an average primary particle size of about 15 nmand an average secondary particle size of 4.5 μm in an amount of 100parts by solid weight and a polyvinyl alcohol having a degree ofpolymerization of 1800 and a degree of saponification of 98.5%(trademark: PVA-117, made by Kuraray Co., Ltd.) in an amount of 30 partsby solid weight, and coated on the laminated paper sheet by using aMayer bar and dried to form an ink-receiving layer having a dry weightof 15 g/m².

Comparative Example III-2

[0312] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous pseudoboehmite coatingdispersion having a solid content of 5% by weight was prepared from apseudoboehmite sol primary particle dispersion (trademark: AS-520, madeby Nissan Kagakukogyo K.K.) having an average primary particle size of10 nm to 100 nm in an amount of 100 parts by solid weight and the samepolyvinyl alcohol (PVA-117) as in Comparative Example III-1 in an amountof 10 parts by solid weight, and coated on the laminated paper sheet byusing a Mayer bar and dried to form an ink-receiving layer having a dryweight of 15 g/m².

Comparative Example III-3

[0313] An ink jet recording sheet was prepared by the same procedures asin Example III-1, except that an aqueous colloidal silica coatingsolution having a solid content of 15% by weight was prepared from acolloidal silica primary particle dispersion (trademark: Snowtex 30,made by Nissan Kagakukogyo K.K.) having an average primary particle sizeof 15 nm in an amount of 50 parts by solid weight and the polyvinylalcohol (PVA-117) in an amount of 100 parts by solid weight, and coatedon the laminated paper sheet by using a Mayer bar and dried to form anink-receiving layer having a dry weight of 15 g/m².

Comparative Example III-4

[0314] A practical gloss ink jet recording sheet (trademark: KH-101,made by Canon Corp.) having an ink-fixing layer formed on a substratesheet and comprising amorphous silica secondary particles having a largesecondary particle size of 1 Mm or more and a gloss layer formed on theink-fixing layer and comprising colloidal silica primary particles wassubjected to the following tests.

[0315] Tests

[0316] The tests were carried out in the same manner as in Example GroupII, with the following exceptions.

[0317] In the test of the ink absorption capacity, the black-colored inkwas solid printed in an ink jetting amount of 18 g/m². The haze volumetest was carried out in the same manner as mentioned above, except thatan ink-receiving layer was coated on a transparent substrate film(trademark: Lumilar T, thickness: 75 μm) and the haze value was measuredby using a reflection color density meter (Model: HR-100, made byMurakami Shikisaigijitsu Kenkyusho). Also, in Example III-9, the inkreceiving layer and the additional ink-absorbent layer laminated on eachother exhibited a total haze value of 41%.

[0318] The test results are shown in Table 3. TABLE 3 Gloss ofInk-absorption solid Haze value Smoothness Content of Ink-absorbingInk-absorption Water Color printed (*)₁ (*)₂ pigment Example No. ratecapacity resistance density portion (%) (sec/10 ml) (wt %) Example III-14 4 4 2.32 3-4  9 12000  71 III-2 4 4 4 1.99 3 36 4200 80 III-3 4 4 41.87 3 51 2700 67 III-4 4 4 4 1.79 3 60 1800 71 III-5 4 4 4 2.14 3 189800 71 III-6 4 4 4 2.37 4 10 41000  71 III-7 3 3 4 2.35 3  8 13000  59III-8 4 4 4 1.70 3 65 1200 71 III-9 4 4 4 2.17 3  8 1100 76 ComparativeIII-1 4 4 2 1.27 1 85  25 77 Example III-2 2 1 4 2.29 3-4  8 13000  91III-3 1 1 1 2.45 2   3.5 — 67 III-4 4 4 4 1.48 2 —  520 —

[0319] Table 3 shows that the ink jet recording sheets of Examples III-1to III-9 in accordance with the present invention exhibited satisfactoryink-absorption properties, the ink receiving layer exhibited high waterresistance, and smoothness and the solid printed ink images had asatisfactory gloss, and a high color density.

Example Group IV Examples IV-1 to IV-15 and Comparative Examples IV-1 toIV-2

[0320] In Example Group IV, the coating amount was indicated by acorresponding dry coating weight. The water content of an ink receivinglayer was indicated by a weight % of water based on the absolute dryweight of the ink receiving layer. For example, when an ink receivinglayer consisted of 100g of an absolute dry solid and 8g of water, thewater content of the ink receiving layer was 8% by weight. Usually, thedry ink receiving layer had a water content of about 8% by weight.

[0321] Also, in Example Group IV, the following pigments were employed.

[0322] (1) Silica colloidal particles A-4

[0323] An aqueous colloidal solution of silica colloidal particles A-4having a concentration of 8% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 14 nm and an average secondary particle size of 2.4 μmand available under a trademark of Mizukasil P-802 from MizusawaKagakukogyo K.K. in water and pulverizing by repeating a combination ofa sand grinder treatment and an ultrasonic homogenizer treatment untilthe average secondary size of the pulverized silica particles reached 70nm.

[0324] (2) Silica colloidal particles B-4

[0325] An aqueous colloidal solution of silica colloidal particles B-4having a concentration of 12% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 15 nm and an average secondary particle size of 2.2 μmand available under a trademark of Mizukasil C-212 from MizusawaKagakukogyo K.K. in water and pulverizing by repeating a combination ofa sand grinder treatment and an ultrasonic homogenizer treatment untilthe average secondary particle size of the pulverized silica particlesreached 200 nm.

[0326] (3) Aluminosilicate colloidal particles B

[0327] An aqueous aluminum silicate colloidal dispersion B having asolid content of 10% by dry weight, was prepared by dispersing syntheticaluminosilicate secondary agglomeration (trademark: Kyowaad 700, made byKyowa Chemical Industries Co., Ltd.) having an average primary particlesize of 3 to 40 nm and an average secondary particle size of 10 μm inwater, and pulverizing by repeating a combination of a sand grindertreatment and an ultrasonic homogenizer treatment until the averagesecondary particle size reached 150 nm.

Example IV-1

[0328] An aqueous colloidal silica coating solution having a solidcontent of 8% by weight was produced from the silica colloidal solutionA-4 in an amount of 100 parts by solid weight, and a polyvinyl alcohol(trademark: PVA-124, made by Kuraray Co., Ltd.) having a degree ofpolymerization of 2400 and a degree of saponification of 98.5% in anamount of 50 parts by solid weight, and coated on a surface of a shapingbase consisting of a polyethylene terephthalate film (trademark: LumilarT, made by Toray Industries Inc.) having a thickness of 75 μm and asurface roughness Ra of 0.02 μm to form a coating layer corresponding toan ink-receiving layer and having a dry weight of 15 g/m².

[0329] A synthetic paper sheet (trademark: Yupo FPG 80, made by Oji YukaGoseishi K.K.) having a basis weight of 60 g/m²) was superposed on andpress-bonded to the coating layer formed on the shaping base at atemperature of 75° C. under a linear pressure of 50 kg/cm by using acalender. Then, the resultant laminate was separated from the shapingbase film, to obtain an ink jet recording sheet.

Example IV-2

[0330] An aqueous colloidal silica coating solution having a solidcontent of 8% by weight was produced from the silica colloidal solutionB-4 in an amount df 100 parts by solid weight, and a polyvinyl alcohol(trademark: PVA-135H, made by Kuraray Co., Ltd.) having a degree ofpolymerization of 3500 and a degree of saponification of 99% or more inan amount of 50 parts by solid weight, and coated on a surface of asynthetic paper sheet (trademark: Yupo FPG 80, made by Oji YukaGoseishi) having a basis weight of 60 g/m², and dried, to form an undercoating layer for an additional ink-absorbent layer having a dry weightof 15 g/m².

[0331] Separately, an aqueous silica colloidal coating solution having asolid content of 8% by weight was prepared from 100 parts by solidweight of the silica colloidal dispersion A-4 and 50 parts by solidweight of the polyvinyl alcohol (PVA-135H), and coated on a surface ofthe same shaping base film as in Example IV-1 to form a coating layercorresponding to an ink-receiving layer and having a dry weight of 15g/m².

[0332] The undercoating layer on the synthetic paper sheet wassuperposed on and press-bonded to the coating layer formed on theshaping base at a temperature of 75° C. under a linear pressure of 50kg/cm by using a calender. Then, the resultant laminate was separatedfrom the shaping base film, to obtain an ink jet recording sheet.

Example IV-3

[0333] An aqueous colloidal silica coating solution having a solidcontent of 8% by weight was produced from the silica colloidaldispersion A-4 in an amount of 100 parts by solid weight, and thepolyvinyl alcohol (PVA-135H) in an amount of 50 parts by solid weight,and coated on a surface of the same shaping base film as in Example IV-1to form a coating layer corresponding to an outermost ink-receivinglayer and having a dry weight of 15 g/m².

[0334] The same ink jet recording sheet as in Example IV-1 composed ofthe synthetic paper sheet and the ink jet receiving layer laminated onthe synthetic paper sheet was superposed on and press-bonded to thecoating layer formed on the shaping base so that the ink receiving layeron the synthetic paper sheet is brought into contact with the coatinglayer on the shaping base film at a temperature of 75° C. under a linearpressure of 50 kg/cm by using a calender. Then, the resultant laminatewas separated from the shaping base film, to obtain an ink jet recordingsheet.

Example IV-4

[0335] An aqueous colloidal silica coating solution having a solidcontent of 8% by weight was produced from the silica colloidaldispersion A-4 in an amount of 100 parts by solid weight, and thepolyvinyl alcohol (PVA-135H) in an amount of 50 parts by solid weight,and coated on a surface of the same synthetic paper sheet (Yupo FPG-80)as in Example IV-2 to form an undercoating coating layer correspondingto an additional ink-absorbent layer and having a dry weight of 15 g/m².

[0336] Separately, an aqueous colloidal silica coating solution having asolid content of 8% by weight was prepared from 100 parts by solidweight of the silica colloidal dispersion A-4 and 50 parts by solidweight of the polyvinyl alcohol (PVA-135H), and coated on a surface ofthe same shaping base film (Lumilar T) as in Example IV-1, to form acoating layer corresponding to an ink-receiving layer and having a dryweight of 15 g/m².

[0337] The undercoat layer formed on the synthetic paper sheet waswetted with water in an amount of 3 g/m² by using a Mayer bar.

[0338] The water-wetted undercoating layer on the synthetic paper sheetwas superposed on and press-bonded to the coating layer on the shapingbase film by using a calender at a temperature of 75° C. under a linearpressure of 50 kg/cm. The resultant laminate was separated from theshaping base film to obtain an ink jet recording sheet.

Example IV-5

[0339] An ink jet recording sheet was produced by the same procedures asin Example IV-1, except that the shaping base film was replaced by ashaping metal drum having chromium-plated and a mirror-finishedperipheral surface with a surface roughness Ra of 0.05 μm.

[0340] The synthetic paper sheet (Yupo FPG80) was superposed on andpress-bonded to the coating layer formed on the shaping drum under alinear pressure of 50 kg/cm, and the resultant laminate was separatedfrom the shaping drum surface, to provide an ink jet recording sheet.

Example IV-6

[0341] An ink jet recording sheet was produced by the same procedures asin Example IV-1, except that the silica colloidal dispersion A-4 wasreplaced by the silica colloidal dispersion B-4.

Example IV-7

[0342] An ink jet recording sheet was produced by the same procedures asin Example IV-1, except that the polyvinyl alcohol (PVA-124) wasreplaced by another polyvinyl alcohol (trademark: PVA-117, made byKuraray Co., Ltd.) having a degree of polymerization of 1800.

Example IV-8

[0343] An ink jet recording sheet was produced by the same procedures asin Example IV-1, except that the polyvinyl alcohol (PVA-124) wasreplaced by another polyvinyl alcohol (trademark: PVA-140H, made byKuraray Co., Ltd.) having a degree of polymerization of 4000.

Example IV-9

[0344] An ink jet recording sheet was produced by the same procedures asin Example IV-1, except that the silica colloidal dispersion A-4 wasreplaced by the aluminosilicate colloidal dispersion B.

Example IV-10

[0345] An ink jet recording sheet was produced by the same procedures asin Example IV-1, except that the aqueous aluminosilicate colloidalcoating solution was prepared from 100 parts by solid weight of thealuminosilicate colloidal dispersion B and 3 parts by solid weight of apolyethylene-polyamine-dicyandiamide condensation reaction product(trademark: PAP-1, made by Nihon Senkakogyo K.K.).

Example IV-11

[0346] An ink jet recording sheet was produced by the same procedures asin Example IV-1, except that the synthetic paper sheet (Yupo FPG 80) wasreplaced by a laminated paper sheet produced by extrusion-laminating acoated paper sheet (trademark: OK Coat, made by Oji Paper Co.) having abasis weight of 127.9 g/m² with a polyethylene resin layer with athickness of 20 μm.

Example IV-12

[0347] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was prepared from the silica colloidaldispersion A-4 in an amount of 100 parts by solid weight and 40 parts byweight of polyvinyl alcohol (available under the trademark of PVA-140H,from Kuraray Co., Ltd.) having a degree of polymerization of 4000 and adegree of saponification of 99% or more.

[0348] The aqueous silica colloidal coating solution was coated on asurface of a shaping base consisting of a polyethylene terephthalatefilm (Lumilar T) having a thickness of 38 μm and a surface roughness Raof 0.02 μm, and dried, to form a coating layer having a dry weight of 15g/m².

[0349] The same aqueous silica colloidal coating solution as mentionedabove was coated on a surface of the laminated paper sheet and dried toform an additional ink-absorbent layer having a dry weight of 15 g/m².The additional ink-absorbent layer was exposed to water vapor to absorbtherein water in an amount of 7.5 g/m², namely to a water content of 50%by weight.

[0350] The water-absorbed additional ink-absorbent layer on thelaminated paper sheet was superposed on and press-bonded to the coatinglayer formed on the shaping base film at a temperature of 50° C. under alinear pressure of 50 kg/cm by using a calender. Then, the resultantlaminate was removed from the shaping base film, to provide an ink jetrecording sheet.

Example IV-13

[0351] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was prepared from 100 parts by solid weight ofthe silica colloidal dispersion A-4 and 50 parts by solid weight of thesame polyvinyl alcohol (PVA-124) as in Example IV-1, and coated on asurface of the same synthetic paper sheet (Yupo FPG-80) as in ExampleIV-1 by using a Mayer bar and dried, to form an ink-receiving layerhaving a dry weight of 15 g/m².

Example IV-4

[0352] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was produced from 100 parts by solid weight ofthe silica colloidal dispersion A-4 and 50 parts by solid weight of thesame polyvinyl alcohol (PVA-124) as in Example IV-1, and coated on asurface of a wood-free paper sheet having a basis weight of 127 g/m² toform a coating layer having a dry coating weight of 15 g/m² ₁ andincompletely dried to such an extent that the dried coating layer had awater content of about 60% by weight.

[0353] A polyethylene terephthalate film (trademark: Lumilar T made byToray) having a thickness of 75 μm and a surface roughness of 0.02 μmwas superposed on the incompletely dried coating layer on the papersheet under pressure, and the laminate was completely dried. Thepolyethylene terephthalate film was removed from the dried laminate, toprovide an ink jet recording sheet.

Example IV-15

[0354] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was prepared from 100 parts by solid weight ofthe silica colloidal dispersion A-4 and 50 parts by solid weight of thepolyvinyl alcohol (PVA-124) as in Example IV-1, and coated on a surfaceof a shaping base consisting of the same polyethylene terephthalate film(Lumilar T) in Example IV-1, and dried to form a coating layercorresponding to an ink-receiving layer and having a dry weight of 8g/m².

[0355] Separately, an aqueous aluminosilicate colloidal coating solutionhaving a solid content of 10% by weight was prepared from 100 parts bysolid weight of the aluminosilicate colloidal dispersion B and 50 partsby solid weight of polyvinyl alcohol (PVA-117), and coated on a surfaceof a wood-free paper sheet having a basis weight of 127 g/m² by using aMayer bar, to form a non-dried coating layer corresponding to anadditional ink-absorbent layer and having a dry weight of 7 g/m².

[0356] The non-dried coating layer on the paper sheet was superposed onthe coating layer on the shaping base film under pressure, and dried (inaccordance with a wet-laminating method). Then the shaping base film wasseparated from the resultant laminate.

[0357] An ink jet recording sheet was obtained.

Comparative Example IV-1

[0358] An aqueous solution of 10% by solid weight of a polyvinyl alcohol(trademark: PVA-117, made by Kuraray Co., Ltd.) was coated on a surfaceof the same laminated paper sheet as in Example IV-11, and dried to forman ink-receiving layer having a dry weight of 10 g/m².

[0359] An ink jet recording sheet was obtained.

Comparative Example IV-2

[0360] A practical ink jet recording gloss sheet (trademark: GP-101,supplied by Canon Corp.) was subjected to the following tests.

[0361] Tests

[0362] The ink jet recording sheets of Examples IV-1 to IV-15 andComparative Examples IV-1 and IV-2 were carried out to the same waterresistance, ink absorption, color density and gloss tests as in ExampleGroup I and the following coating layer bonding strength and smoothnesstests.

[0363] In the measurement of the ink absorption capacity of the inkreceiving layer, yellow-, magenta-, and cyan- colored inks weresuccessively solid printed in a total amount of 25 g/m² on a square areaof 10 cm×10 cm of the ink receiving layer.

[0364] [Coating Layer Bonding Strength]

[0365] An adhesive tape was adhered to the surface of the ink-receivinglayer of the ink jet recording sheet, lightly pressed by hand and thenremoved.

[0366] The test results were evaluated in the following four classes.

[0367] 4: No change appeared in the ink-receiving layer.

[0368] 3: A very small portion of the ink-receiving layer was removed,and the remaining ink-receiving layer is still usable for practice.

[0369] 2: The ink-receiving layer was partially removed.

[0370] 1: Almost all of the ink-receiving layer was removed.

[0371] [Coating Layer Smoothness]

[0372] The smoothness of the ink-receiving layer of the ink jetrecording sheet was observed by the naked eye and evaluated in thefollowing three classes.

[0373] 3; The surface of the ink-receiving layer was quite smooth.

[0374] 2: The ink-receiving layer surface was lightly roughened.

[0375] 1: The ink-receiving layer surface was certainly roughened, andhad a bad appearance.

[0376] The test results are shown in Table 4. TABLE 4 Ink-absorptionGloss of Coating layer Coating Ink-absorbing Ink-absorption Waterprinted bonding layer Example No. rate capacity resistance Color densityink images strength smoothness Example IV-1 4 3 4 2.15 4 4 3 IV-2 4 4 42.13 4 3 3 IV-3 4 4 4 2.15 4 3 3 IV-4 4 4 4 2.16 4 4 3 IV-5 4 3 4 2.15 44 3 IV-6 4 3 4 1.75 4 4 3 IV-7 4 3 3 2.18 4 4 3 IV-8 4 3 4 2.17 4 4 3IV-9 4 3 4 1.82 4 4 3  IV-10 4 3 4 1.84 4 4 3  IV-11 4 3 4 2.13 4 4 3 IV-12 4 4 4 2.14 3 3 3  IV-13 4 3 4 2.12 3 2 2  IV-14 4 3 4 2.16 3 2 2 IV-15 4 3 3 2.11 3 2 2 Comparative IV-1 1 1 1 2.31 1 2 2 Example IV-2 44 4 1.42 1 1 2

[0377] Table 4 clearly shows that the ink jet recording sheets ofExamples IV-1 to IV-15 in accordance with the present invention weresatisfactory in all of the tested results.

Example Group V Examples V-1 to V-5 and Comparative Examples V-1 and V-3

[0378] In Example Group V, the following pigments were employed.

[0379] (1) Silica colloidal particles A-5

[0380] An aqueous colloidal solution of silica colloidal particles A-5having a concentration of 8% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 11 nm and an average secondary particle size of 3 μmand available under a trademark of Nipsil HD-2 from Nihon Silica KogyoK.K. in water, and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary particle size of the pulverized silica particlesreached 30 nm.

[0381] (2) Silica colloidal particles B-5

[0382] An aqueous colloidal solution of silica colloidal particles B-5having a concentration of 8% by weight was prepared by dispersing wetmethod synthetic amorphous silica particles having an average primaryparticle size of 16 nm and an average secondary particle size of 9 μmand available under a trademark of Nipsil LP from Nihon Silica KogyoK.K. in water and pulverizing by repeating a combination of a sandgrinder treatment and an ultrasonic homogenizer treatment until theaverage secondary particle size of the pulverized silica particlesreached 50 nm.

Example V-1

[0383] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was prepared from 100 parts by solid weight ofthe silica colloidal dispersion A-5 and 40 parts by solid weight of apolyvinyl alcohol (trademark: PVA-124, made by Kuraray Co., Ltd.) havinga degree of polymerization of 2400 and a degree of saponification of98.5%, and coated on a surface of a transparent polyethyleneterephthalate (PET) film (trademark: Merinex D535, made by ICI) having athickness of 100 μm and a haze value of 0.5% by using a Mayer bar anddried to form an ink-receiving layer having a dry weight of 20 g/m². Anink jet recording sheet was obtained.

Example V-2

[0384] An aqueous silica colloidal coating solution having a solidcontent of 12% by weight was prepared from 100 parts by solid weight ofthe silica colloidal dispersion B-5 and 40 parts by solid weight of apolyvinyl alcohol (trademark: PVA-124, made by Kuraray Co., Ltd.) havinga degree of polymerization of 2400 and a degree of saponification of98.5%, and coated on a surface of a transparent polyethyleneterephthalate (PET) film (trademark: Merinex D535, made by ICI) having athickness of 100 μm and a haze value of 0.5% by using a Mayer bar anddried to form an ink-receiving layer having a dry weight of 20 g/m². Anink jet recording sheet was obtained.

Example V-3

[0385] An aqueous silica colloidal coating solution having a solidcontent of 10% by weight was prepared from 100 parts by solid weight ofthe silica colloidal dispersion A-5 and 40 parts by solid weight of apolyvinyl alcohol (trademark: PVA-117, made by Kuraray Co., Ltd.) havinga degree of polymerization of 1800 and a degree of saponification of98.5%, and coated on a surface of a transparent polyethyleneterephthalate (PET) film (trademark: Merinex D535, made by ICI) having athickness of 100 μm and a haze value of 0.5% by using a Mayer bar anddried to form an ink-receiving layer having a dry weight of 20 g/m². Anink jet recording sheet was obtained.

Example V-4

[0386] An aqueous silica colloidal coating solution having a solidcontent of 8% by weight was prepared from 100 parts by solid weight ofthe silica colloidal dispersion A-5 and 40 parts by solid weight of apolyvinyl alcohol (trademark: PVA-235, made by Kuraray Co., Ltd.) havinga degree of polymerization of 3500 and a degree of saponification of88.0%, and coated on a surface of a transparent polyethyleneterephthalate (PET) film (trademark: Merinex D535, made by ICI) having athickness of 100 tm and a haze value of 0.5% by using a Mayer bar anddried to form an ink-receiving layer having a dry weight of 20 g/m². Anink jet recording sheet was obtained.

Comparative Example V-1

[0387] An aqueous silica coating solution having a solid content of 15%by weight was prepared from 100 parts by solid weight of a wet methodsynthetic amorphous silica (trademark: Nipsil HD-2, made by NihonSilicakogyo K.K.) having an average primary particle size of 11 nm andan average secondary particle size of 3 μm and 40 parts by solid weightof a polyvinyl alcohol (trademark: PVA-124, made by Kuraray Co., Ltd.)having a degree of polymerization of 2400 and a degree of saponificationof 98.5%, and coated on a surface of a transparent polyethyleneterephthalate (PET) film (trademark: Merinex D535, made by ICI) having athickness of 100 μm and a haze value of 0.5% by using a Mayer bar anddried to form an ink-receiving layer having a dry weight of 20 g/m². Anink jet recording sheet was obtained.

Comparative Example V-2

[0388] An aqueous solution of 10% by solid weight of a polyvinyl alcohol(trademark: PVA-117, made by Kuraray Co., Ltd.) having a degree ofpolymerization of 1800 and a degree of saponification of 98.5% wascoated on a surface of a transparent polyethylene terephthalate (PET)film (trademark: Merinex D535, made by ICI) having a thickness of 100 μmand a haze value of 0.5% and dried to form an ink-receiving layer havinga dry weight of 20 g/m². An ink jet recording sheet was obtained.

Comparative Example V-3

[0389] An aqueous silica colloidal coating solution having a solidcontent of 20% by weight was prepared from 100 parts by solid weight ofthe silica colloidal dispersion A-5 and 80 parts by solid weight of astyrene-butadiene copolymer latex (trademark: D693, made by NihonGoseigomu K.K.), and coated on a surface of a transparent polyethyleneterephthalate (PET) film (trademark: Merinex D535, made by ICI) having athickness of 100 μm and a haze value of 0.5% by using a Mayer bar anddried to form an ink-receiving layer having a dry weight of 20 g/m². Anink jet recording sheet was obtained.

[0390] Tests

[0391] The ink jet recording sheets of Examples V-1 to V-4 andComparative Examples V-1 and V-3 were subjected to the following tests.

[0392] The ink jet printing procedure was carried out by using apractical ink jet printer (trademark: BJC-600J, made by Canon Corp.).

[0393] [Haze Value (Transparency)]

[0394] The haze value was determined in accordance with JISK 7105 byusing a haze value meter (model: HR-100) made by MurakamiShikisaigijitsu Kenkyusho.

[0395] [Water Resistance]

[0396] A water drop was put on a surface of the ink-receiving layer ofthe specimen, 30 minutes after the water drop-putting, the water dropwas wiped off, and the water-wetted portion of the ink-receiving waterwas rubbed by a finger and the results were observed by the naked eyeand evaluated in the following three classes.

[0397] 3: No change in the ink-receiving layer was found.

[0398] 2: The ink-receiving layer was partially removed.

[0399] 1: The ink receiving layer was completely removed.

[0400] [Ink Absorbing Rate (Ink Drying Rate)]

[0401] Each of black, yellow, magenta and cyan-colored inks was solidprinted on the ink-receiving layer of the specimen, immediately every 5seconds after the printing, a wood-free paper sheet was superposed onthe ink-printed portion of the specimen and the transfer of the ink tothe paper sheet was observed. The time necessary to completely fix theprinted ink in the ink receiving layer and to cause the printed ink notto be transferred to the paper sheet, was determined. The test resultswere evaluated in the following four classes.

[0402] 4: The ink-fixing time was less than 5 seconds.

[0403] 3: The ink-fixing time was 5 seconds or more but less than 10seconds.

[0404] 2: The ink-fixing time was 10 seconds or more but less than 50seconds.

[0405] 1: The ink-fixing time was 50 seconds or more.

[0406] [Color density]

[0407] A solid printed specimen was placed on a coated paper sheet andthe color density of the solid ink images on the specimen was measuredby Macbeth reflection color density tester (model: RD-920). The colordensity of the ink images was indicated by an average value of fivemeasurement results.

[0408] [OHP Projection]

[0409] Ink images formed on the specimen was projected onto an OHP, andthe sharpness of the projected images was observed by the naked eye andevaluated in the following four classes.

[0410] 4: The background was light and the projected images were veryclear.

[0411] 3: The background was slightly dark and the projected images wereclear and practically satisfactory.

[0412] 2: The background was certainly dark and the clarity of theprojected images was unsatisfactory.

[0413] 1: The background was quite dark and the projected, images wereunclear.

[0414] The test results are shown in Table 5. TABLE 5 Haze Ink valueWater absorbing Color OHP Example No. (%) resistance rate densityprojection Example V-1 8 3 4 2.2 4 V-2 16  3 4 2.1 3 V-3 8 2 4 2.2 4 V-48 2 4 2.2 4 Comparative V-1 85  2 4 1.3 1 Example V-2 1 1 1 2.3 4 V-312  3 1 1.8 3

[0415] Table 5 shows that the ink jet recording sheets of Examples V-1to V-4 in accordance with the present invention had a high transparency,a satisfactory water resistance, a satisfactory ink-absorption property,and a high color density of ink images and was usable for over headprojection (OHP).

We claim:
 1. An ink jet recording material comprising: a substrate; andan ink-receiving layer formed on at least one surface of the substrate,wherein the ink-receiving layer comprises a binder, and a plurality ofsecondary particles, wherein the secondary particles have an averagesecondary particle size of 10 to 300 nm, each of the secondary particlesconsisting essentially of a plurality of primary particles of at leastone member selected from the group consisting of silica prepared by wetmethod, which silica will be referred to as wet method silicahereinafter, and aluminosilicate, and wherein the primary particles areagglomerated with each other to form the secondary particles by anattraction force including hydrogen bonding force between silanol groupslocated on the surfaces of the primary particles and van der Waals forcebetween the primary particles, in each of the secondary particles, poresbeing formed between the agglomerated primary particles.
 2. The ink jetrecording material as claimed in claim 1, wherein the binder for theink-receiving layer comprises water-soluble resin.
 3. The ink jetrecording material as claimed in claim 1, wherein the secondaryparticles each consist essentially of a plurality of silica primaryparticles are those prepared from agglomerated silica particles by abreaking down method by which the average secondary particle size isadjusted to 10 to 300 nm.
 4. The ink jet recording material as claimedin claim 1, wherein the primary particles of wet method silica andaluminosilicate have an average primary particle size of 3 to 40 nm. 5.The ink jet recording material as claimed in claim 1, wherein theink-receiving layer has a plurality of pores formed therein and exhibitsa pore radius distribution curve having a peak corresponding to a poreradius of about 40 nm or less.
 6. The ink jet recording material asclaimed in claim 5, wherein at least one additional ink-absorbent layercomprising a binder resin and a plurality of pigment particles, isformed between the substrate and the ink-receiving layer.
 7. The ink jetrecording material as claimed in claim 5, wherein the binder for theadditional ink-absorbent layer comprises a water-soluble resin.
 8. Theink jet recording material as claimed in claim 5, wherein the secondaryparticles are each composed essentially of a plurality of primaryparticles having an average primary particle size of 3 to 40 nm andagglomerated with each other, and have an average secondary particlesize of 10 to 150 nm.
 9. The ink jet recording material as claimed inclaim 2 or 7, wherein the water-soluble resin comprises a polyvinylalcohol having an degree of polymerization of 2,000 or more.
 10. The inkjet recording material as claimed in claim 2 or 7, wherein thewater-soluble resin comprises a polyvinyl alcohol having a degree ofsaponification of 95% or more.
 11. The ink jet recording material asclaimed in claim 5, wherein the ink-receiving layer has a plurality ofpores formed therein, and exhibits an integrated pore volume of all thepores of 0.6 ml/g or more, and a total volume of the pores with a poreradius of 3 to 20 nm of 0.3 ml/g or more.
 12. The ink jet recordingmaterial as claimed in claim 1, wherein at least one additionalink-absorbent layer, comprising a binder resin and a plurality ofpigment particles, is formed between the substrate and the ink-receivinglayer.
 13. The ink jet recording material as claimed in claim 1, whereinthe ink receiving layer has a haze value of 4 to 65%.
 14. The inkreceiving layer as claimed in claim 13, wherein the binder for theink-receiving layer comprises a water-soluble resin.
 15. The ink jetrecording material as claimed in claim 13, wherein the secondaryparticles are each composed essentially of a plurality of primaryparticles having an average primary particle size of 3 to 40 nm andagglomerated with each other, and have an average secondary particlesize of 10 to 200 nm.
 16. The ink jet recording material as claimed inclaim 13, wherein at least one additional ink-absorbent layer comprisinga binder resin and a plurality of pigment particles is formed betweenthe substrate and the ink receiving layer.
 17. The ink jet recordingmaterial as claimed in claim 1, wherein the substrate is transparent.18. The ink jet recording material as claimed in claim 17, wherein theink-receiving layer formed on the transparent substrate surfacecomprises the secondary particles having an average secondary particlesize of 10 to 100 nm and formed from the primary particles of at leastone member selected from the group consisting of wet method silica andaluminosilicate, having an average primary particle size of 3 to 30 nm.19. The ink jet recording material as claimed in claim 17 or 18, havinga haze value of 20% or less.
 20. The ink jet recording material asclaimed in claim 1, wherein the substrate is bonded to the ink-receivinglayer through an intermediate layer comprising a member selected fromthe group consisting of bonding materials and adhesive materials. 21.The ink jet recording material as claimed in claim 1, wherein theprimary particles for the secondary particles for the ink-receivinglayer are those of the wet method silica.
 22. The ink jet recordingmaterial as claimed in claim 1, wherein the primary particles areagglomerated with each other to form the secondary particles without anybinder.
 23. A process for producing an ink jet recording material,comprising the steps of: forming an ink-receiving layer comprising abinder, and a plurality of secondary particles having an averagesecondary particle size of 500 nm or less and each comprising aplurality of primary particles of at least one member selected from thegroup consisting of silica and aluminosilicate, and agglomerated witheach other to form the secondary particles, on a surface of a shapingbase; bonding the substrate to the ink-receiving layer provided on theshaping base to form a laminate; and separating the resultant laminatefrom the shaping base.
 24. The process as claimed in claim 23, whereinthe secondary particles have an average secondary particle size of 10 to300 nm.
 25. The process as claimed in claim 23, wherein the primaryparticles of silica and aluminosilicate have an average primary particlesize of 3 to 40 nm.
 26. The process as claimed in claim 23, wherein thesubstrate is bonded to the ink-receiving layer provided on the shapingbase through a member selected from the group consisting of bondingmaterials and adhesive materials.
 27. The process as claimed in claim23, wherein the step of bonding the substrate to the ink receiving layeris carried out by wetting the surface of the ink receiving layer withwater or water vapor, and then press-bonding the substrate to thesurface-wetted receiving layer to provide a laminate.
 28. The process asclaimed in claim 23, further comprising the step of forming anadditional ink-absorbent layer comprising a binder and pigment particleson a surface of the substrate before the bonding step, the additionalink-absorbing layer provided on the substrate being bonded to theink-receiving layer provided on the shaping base.
 29. The process asclaimed in claim 28, wherein the bonding step is carried out by wettingat least one of the ink-receiving layer provided on the shaping base andthe additional ink-absorbent layer provided on the substrate with wateror water vapor, and then press-bonding the additional ink-absorbentlayer on the substrate and the ink-receiving layer on the shaping base,to provide a laminate.
 30. The process as claimed in claim 23, furthercomprising the step of forming an additional ink-absorbent layercomprising a binder and pigment particles on a surface of the inkreceiving layer before the bonding step, the additional ink-absorbinglayer provided on the ink receiving layer being bonded to the substrate.31. The process as claimed in claim 30, wherein the bonding step iscarried out by wetting the additional ink-absorbent layer provided onthe ink receiving layer with water or water vapor, and thenpress-bonding the additional ink-absorbent layer and the ink-receivinglayer on the shaping base, to provide a laminate.
 32. The process asclaimed in claim 23, wherein the binder for the ink-receiving layercomprises a water-soluble resin.